Reason Your Way to Right Answers on Hard GMAT Math Questions

[@dominatethegmat]

Ready to dominate the GMAT? Try us FREE and see for yourself why students trust DTP for their GMAT Prep. Start your Free Trial: www.dominatetestprep.com/offers/VYpvBfXa

[@N1GHTWOLF1]

lol i didn't even know what the question was asking im fukd

[@dominatethegmat]

Now you know! That's all part of learning and improvement. Hope you found it helpful!

[@mdgamble]

I was like..... what you say? Whose unit and whose digit and who is who

[@xiction]

Me too lol

[@ryankoech]

@@xiction sorry

[@ethandever6462]

Finding out that my method to get the answer was the exact same as the one you taught was soooooooooooo satisfying!

[@dominatethegmat]

That's awesome! "Great minds..." as they say.

[@pigmon2212]

OMG I can never understand the cycle they explain on Internet but you smh make it so simple. Thanks a lot....Love

[@dominatethegmat]

Great to hear, Nhu. I'm glad you found this video helpful!

[@Just-ing]

The way you've laid it, it's imprinted in my conscience. Thank You Sir

[@dominatethegmat]

That's awesome. Glad it helped!

[@matheusmascarenhas]

I got to this video without any prep. Knowing GMAT is about reasoning, my first attempt was quite close to the reasoning process you explained. Thanks!

[@dominatethegmat]

That's awesome! Best of luck to you with the rest of your prep and let me know how else I can help.

[@meganmcgee5668]

This is perfect, I love the way you explain things and keep everything organized. Thank you so much!

[@dominatethegmat]

My pleasure, glad it helped!

[@conceptofbasictoadvanced3587]

Hii

[@wombats2024]

i like u meg

[@hlabanastudios10]

I'm taking my GMAT in like 3 days from now and just seeing this really helped me to remember that I need to work around the box instead of tryignto answers the probelm insted

[@dominatethegmat]

Thank you for sharing. I'm glad you found this video at just the right time. For additional last-minute tips, I think you'll find this podcast episode helpful: podcast.dominatetestprep.com/548431/4566068-27-7-days-out-from-test-day . Good luck and let us know how it goes!

[@WeBreakItAllDownRightHere]

REASON WILL PREVAIL

[@GameSplained]

I got that answer from a completely different reasoning, but that is fantastic. Seeing it shown helps me understand that I need to keep going.

[@dominatethegmat]

There are often multiple ways to get to a right answer, and I'm glad this showed you an alternative way that might come in handy for you (and save you some time!) on test day. Good luck and don't hesitate to let me know how else we can help.

[@mcloving_]

when you said we should try it . i just sub 7-3 (since they were the units of both) and had 4. Your approach was awesome even though mine was just a guess

[@dominatethegmat]

That's similar to what Hajumula did (see below). You can see my response to him and why that's not the right approach. But good guesses are always a plus on test day!

[@luu3884]

Thank you. I come from a traditional math background and I couldn’t figure out what was being asked but in the end I came out enlightened. I see that it’s about thinking of a different way to get to the answer, master reasoning and find the pattern.

[@dominatethegmat]

That's exactly right! There are certainly quantitative questions on the GMAT that can be solved using traditional math, but adopting the "reasoning" mindset can help you on quite a few questions as well. Good luck and let me know how else I can help!

[@vinitasangar7777]

This is just the perfect channel for prep

[@dominatethegmat]

Thank you. And our complete courses are even more perfect! 😀 Thanks for sharing your encouraging comment, and best of luck to you as you continue preparing for the GMAT. Let us know how else we can help.

[@joisarpayal81]

This is extremely helpful. Thank you so much. Best channel on KZbin I have come across for Gmat prep ☺️

[@dominatethegmat]

Thank you for the kind words. I'm glad you're enjoying the content!

[@zlutmundt7334]

Awesome. Best GMAT channel on YT

[@dominatethegmat]

Zlut mundt Thanks!

[@zbear84]

Thanks for this video! I really enjoyed it. I managed to reason that the answer had to be either C or D, because the units digit would have to be even since both terms would always be odd, but I wasn't quite patient enough to work out the answer on my own. Your approach was eye-opening!

[@dominatethegmat]

I'm glad to hear it, Zach. And I'm also glad to hear that you wrestled with it on your own first before watching my solution. That's how true learning and breakthrough happen (I actually talk about this in our most recent podcast episode: podcast.dominatetestprep.com/548431/12102578-64-the-secret-to-growing-past-a-prep-plateau). Good luck and let me know how else we can help!

[@manikshreya]

Faster way could be to divide the power by 4 n then put the remainder to the units digit.eg. 133^23 will be 23/4 so remainder is 3 , then unit's digit of 133 is 3 so 3^3 will give 27 n unit digits is 7

[@yuneecorn]

This was super helpful, SO MUCH BETTER than just reading the written explanations as that gets confusing sometimes too. Thank you for the tutorial! Gonna check out your website as well,!

[@dominatethegmat]

Awesome, glad you found it helpful! I know you'll find my other lessons and comprehensive courses even more so. Let me know if you have any questions and how else I can help.

[@edwardbudihardjo2105]

I am really interested in taking GMAT because I want to pursue an MBA in the near future. I came across your video and it was amazing! I love the way you explain it in detail and make me want to participate in your classroom. It helps me a lot! Thank you for sharing your knowledge and educate us (GMAT for dummies).

[@dominatethegmat]

My pleasure, I'm glad you found this video helpful. How much time do you have before you take the GMAT? And what are your target schools? Let me know if you want more info about my comprehensive courses, and let me know how else I can help!

[@edwardbudihardjo2105]

@@dominatethegmat Thank you for replying. To be honest, I don't have an exact time-frame. I still am looking for a business related career or position especially in finance. My target schools are Wharton, HBS, and Chicago Booth. I looked at your website and I liked it. Will definitely reach out back to you when the time arises.

[@dominatethegmat]

@@edwardbudihardjo2105 Sounds great. I'll look forward to hearing from you.

[@mikepod637]

thanks man, kinda nuts you still respond to ur audiences questions 22 months after posting the video. Def will check out other videos.

[@dominatethegmat]

You're welcome! And yeah, it's important that people know the content is still relevant and that we pride ourselves on great customer service at Dominate Test Prep. Enjoy the rest of the videos on this channel and check out our full courses whenever you're ready to dive deeper. Good luck and let me know how else I can help!

[@jinghaowang10]

Extremely helpful method! Great to know!

[@dominatethegmat]

Awesome, glad it helped!

[@ant0n5599]

Really thankful for this video, opened up my eyes to the kind of prep I need.

[@dominatethegmat]

Thanks for sharing. Glad it helped!

[@british021]

Great video! I’m about to start prep for the GMAT and I assume from my learning style that I will find it difficult to answer the tougher questions in approx 1 min. How can you do this method in under 1 minute? Practise practise practise I guess? Additionally, given your experience, would you say the difficulty of the question is correlated with the time needed to answer? E.g. the earlier “easier” questions should hypothetically take 20/30 seconds thus allocating more time for the later ones. Of course it also depends on your strengths, but just in general terms Appreciate the video! The reason I am fond of math is in part due to the reasoning and how it all fits in nicely once you’ve learnt the tricks and patterns such as the one demonstrated here. Cheers

[@dominatethegmat]

I'm glad you found us, Joseph! First of all, you have 62 minutes to complete 31 questions on the quant section, meaning you have 2 minutes per question, not 1. So hopefully that makes you feel a little better. In terms of solving questions more quickly, a lot of it comes down to pattern recognition. Whether the question is easy or hard, if you're able to quickly deduce the type of question you're dealing with and the best strategy for attacking it, you should be able to complete even the harder questions in under 2 minutes. I teach all of those best strategies and approaches in my course: www.dominatethegmat.com/video-purchase/full-gmat-prep-course/. I hope to have the opportunity to work with you!

[@Learnwithsaba74]

u are awesome! I'm from Iran- Tehran and i have Applied for MBA Exam, that would be on may and i really appreciate you,cuz i was a little weak on this section now i can easily solve this type of questions

[@dominatethegmat]

Great to hear, Saba! I'm glad you found this channel and whenever you're ready to dive deeper into the other concepts and strategies you'll need to dominate the GMAT, consider one of our comprehensive courses: www.dominatethegmat.com/video-purchase/full-gmat-prep-course/. In the meantime, don't hesitate to let me know how else I can help!

[@ohriven1484]

I'm bored, so I decided to look for some random gmat exercises to understand what I will have to face next year. I'm glad I managed to solve it by myself lol reasoning tests are the only reason I managed to get into a prestigious university in the first place

[@dominatethegmat]

That's great! If you do commit to the GMAT, don't underestimate it. Even if you've been historically good at reasoning tests, there are still patterns and question types that you'll want to get up to speed on to get a great score. Good luck and let me know how else I can help!

[@kvin9210]

Which university did you get into?

[@christianlira1259]

Wow and thank you for this great lesson. Watch the entire video, and for the re-cap/view start @ 05:32 min/sec + final working steps and thinking are crucial to get the correct answer as GMAT answers are designed to distract. Thank you Brett.

[@dominatethegmat]

Glad you're enjoying these video lessons. Best of luck to you as you continue preparing for the GMAT, and if you want to dive deeper, I hope you'll consider one of our comprehensive courses. In the meantime...study hard!

[@iOver]

He's really there to help us. Thank you so much. You are really giving us hope when we struggle during our preparation

[@dominatethegmat]

You're welcome! I'm glad you found this video helpful. Let me know if you need anything else.

[@tx_94]

wow, so profound, this came in clutch. Thank you!

[@dominatethegmat]

My pleasure. Glad you found it at just the right time!

[@1800TheSaraShow]

This is the kind of person we need 💪

[@dominatethegmat]

I appreciate that!

[@hansoreva1]

Is it weird that soon as the answer popped just subtract 7 from 3 and instinctively knew it's 4... The reasoning is so amazing I had an idea but now I feel I fully understand ...👍🏽👍🏽

[@dominatethegmat]

That's great to hear, Hans!

[@hma9531]

Did you mean the fast way is to know the first unit of the first multiplication of each 177 & 133 by them self Separately and then this method valid always¿¡

[@dominatethegmat]

@@hma9531 Yes, that's right. Only the first 7 and 3 matter from a "units digit" standpoint when determining the units digit of the final product.

[@manafro2714]

Very well-made video, thank you very much! I have learned a lot, even though I don't plan to take the GMAT (I'm just looking for tools to develop my thinking).

[@dominatethegmat]

Awesome, glad you found it helpful! If that's your goal, you might also want to check out a book by Brandon Royal called "The Little Blue Reasoning Book." I often recommend it to my GMAT students, as it helps with critical thinking.

[@brunoedmundo7521]

Thanks for all the work you put to help other people. This is definitely helping me.

[@dominatethegmat]

Glad to hear it! You're welcome. Best of luck to you and don't hesitate to let me know how else I can help.

[@suringandhi3026]

Thanks very helpful. I have been binge watching all your lessons.

[@dominatethegmat]

Great, Surin. I'm glad you found this (and my other videos) helpful. I know you'll love our full course content even more. I'm hope to be able to continue working with you!

[@elainejjj]

Thank you, sir! You made the explanation super clear

[@dominatethegmat]

You're welcome. Glad it helped!

[@ACCA_UK]

Hey mate, your method is fairly reasonable, but I would like to share another more time-efficient one. What if we subtract the last digit (7)-(3) we get =4 and the same thing with exponents (28)-(23)=5 so basically it is 4^5 = 1024 ends in a 4. and hardly takes less than 30 sec.

[@dominatethegmat]

Your approach won't always work. What if the second term ends in, say, a 9 instead of a 3? Now subtracting the last digits results in -2. As another example, try your method for 6^5 - 4^3. According to your approach, it should be the same as (6-4)^(5-3). But it's not.

[@nataliadron8474]

Many years ago we used to learn this approach at mid school

[@dominatethegmat]

That's awesome... first, that you were actually taught this approach in school, and second, that you still remember it!

[@rahulnimse2620]

There can be only one digit from 9 digits at unit place. So use below technique to solve any problem. Cyclicity of 1, 5 and 6: Any power of 1, 5 and 6 will end respectively with 1, 5 and 6 (irrespective of the power).Thus the digits1,5 and 6 are said to have a cyclicity of 1 and finding the unit digit of their power is not an issue. ================================= Cyclicity of 4 and 9: The digit 4 and 9 have a cyclicity of 2 i.e. two different values of the unit digit get repeated, as the powers of 4 and 9 are increased successively. Cycle of unit digit of 4n as n takes values 1, 2, 3, 4, 5, …… is: 4, 6, 4, 6, 4, …… Cycle of unit digit of 9n as n takes values 1, 2, 3, 4, 5, …… is: 9, 1, 9, 1, 9, …… Thus in the case of 4n and 9n one just needs to check if n is odd or even and accordingly the unit digit can be found. ================================= Cyclicity of 2, 3, 7 and 8: Each of these digits has a cycle of 4 and the respective cycles are… As n assumes successive natural numbers 1, 2, 3, 4, 5, …… …… unit digit of 2n will be 2, 4, 8, 6,....2,4,8,6 unit digit of 3n will be 3, 9, 7, 1, ...3,9,7,1 unit digit of 7n will be 7, 9, 3, 1, ….7,9,3,1 unit digit of 8n will be 8, 4, 2, 6, ....8,4,2,6

[@chunlianli465]

Whow!!!! Realllly easy to understand ~!Thanks. And its really interesting to learn .

[@dominatethegmat]

You're welcome. Glad you found this helpful!

[@D_88_ELCAP]

Mind BLOWN!

[@dominatethegmat]

Glad you liked it!

[@Jordanhello234]

Thanks I was going to multiply all of the powers and the throw the test in garbage as it would have been too overwhelming.

[@dominatethegmat]

Haha, yeah, if you ever find yourself doing lots of long arithmetic on the GMAT, you've probably missed something. Glad this helped!

[@curiousglasses8924]

So helpful! Continue the good work!

[@dominatethegmat]

Thank you! I'm glad you found this video helpful.

[@TheVikasV3]

You are great teacher ! ❤️🔥 😀

[@dominatethegmat]

Thank you, I appreciate that!

[@ejazhunzai]

A perfect way to prepare for GMAT. Thumbs up..

[@dominatethegmat]

Awesome, glad you found us!

[@Rubens_991]

Nice solving. Impossible in 2min if you ask me.

[@dominatethegmat]

Thank you! And now that you know the best approach on a problem like this, you should have no problem solving similar questions in less than 2 minutes in the future. Best of luck to you!

[@ahmedbhatkar4623]

EXCELLENT EXPLANATION

[@dominatethegmat]

Thank you. I'm glad you found it helpful!

[@shrinivaskottawar2068]

Nicely explained..!!!

[@dominatethegmat]

Thank you. Glad you found it helpful!

[@s_tv2312]

Loved this video

[@dominatethegmat]

Glad to hear it! Let me know how else I can help.

[@dipanjansaha7931]

Man, you are amazing!!

[@dominatethegmat]

Thank you!

[@doniyorbeknabijonov3222]

yes , very useful video.. thank you

[@A10S10001]

Good video. Eventough you must need to reason your way through the exam. Theorems and formulas vill indeed be needed. Im studying the OG of 2018 along with GMAT club.First , im advancing at my pace with the 400+ exercises per section. After that Im planing to solve the OG 2019 and 2017 , fighting against the clock. Is my plan Ok? Where can i take a full online practice test?

[@dominatethegmat]

There are two free practice tests available through mba.com. You can also get up to five more on my website here: www.dominatethegmat.com/gmat-online-practice-test/gmat-online-practice-test/. As for your study plan, just make sure you're learning the content and strategy correctly so that all of your practice is engraining good habits instead of bad. Remember my 3-part success triad: Content - Strategy - Practice. It sounds like you're focusing on the last part, but the first two parts are what will ensure your practice is as effective as possible.

[@hv5304]

Great presentation! Gmat is interesting...

[@dominatethegmat]

Thank you! Glad you found it helpful.

[@bikramsingh7768]

Hi Brandon. Great video. Is your book, 'Ace the GMAT' current with the GMAT of 2022 ? Thank you.

[@dominatethegmat]

I just double-checked with Brandon Royal and "yes," the latest version of his "Ace the GMAT" is relevant for the 2022 GMAT exam.

[@bikramsingh7768]

@@dominatethegmat Good. Can you send me a link please ? Can't find the latest version on amazon.in (India). Thank you.

[@bikramsingh7768]

Is there a 2022 edition ? Thank you.

[@dominatethegmat]

@@bikramsingh7768 No, Brandon doesn't update "Ace the GMAT" every year (no need). Even the GMAC is going to stop putting out a new edition of the GMAT Official Guide every year. The exam simply doesn't change significantly from year to year.

[@dominatethegmat]

@@bikramsingh7768 Here you go: amzn.to/3s6WXdO

[@ojomona_]

Whoa!!!!! Consider my mind blown!

[@dominatethegmat]

Glad to hear it! Progress.

[@ndeyebinetasylla2857]

I love this! Definitely helpful

[@dominatethegmat]

Awesome Ndeye! Thanks for taking the time to leave a comment. Good luck and let me know how else I can help!

[@bobo0991]

This is amazing. Thank you

[@dominatethegmat]

My pleasure. Glad you found it helpful!

[@michaelfink6748]

177-133= 44. 28-23=5. 44^5= 164,916,224. This is how I came to the answer. This way seems far easier but I guess it was just a coincidence they both ended in 4.

[@dominatethegmat]

I don't fully follow your logic but it does appear to be coincidence. And how did you get 44^5 without a calculator? That's a lot of unnecessary computation!

[@ryankoech]

@@dominatethegmat is it bad to use a calculator?

[@dominatethegmat]

@@ryankoech You're not allowed to use a calculator on the Quantitative Reasoning section of the GMAT. So you don't want to practice with a calculator since you won't be able to use it on test day.

[@ryankoech]

@@dominatethegmat thanks for clarifying

[@jayanirachithra9050]

It is amazing and well explained. ❤

[@dominatethegmat]

Thank you. Glad you found it helpful!

[@rezairdha2]

What is the exact meaning of unit digits? I dont understand the question.

[@dominatethegmat]

The unit's digit is the digit in the one's column of a number. In the number 68, for example, 8 is the unit's digit (and 6 is the tens digit since it's in the ten's column).

[@tadellegina9469]

Wow amazing thank you

[@dominatethegmat]

You're welcome. Glad you found it helpful!

[@LuisTorresadboy13]

This is really awesome

[@dominatethegmat]

Glad you enjoyed it, Luis!

[@swarnadeeproy2309]

Loved the approach

[@dominatethegmat]

Thanks, glad it helped!

[@Bloopiies]

Hello, I was curious, is there a difference in the GMAT exam content in the United States and Canada? If so, will this course benefit me as I am a Canadian that intends to write the GMAT in Canada? Furthermore, my high school math is extremely weak, I have forgotten most of it, will I be able to learn the basics from the ground up necessary for the GMAT through this course? Thank you, Zulfiqaar Baksh

[@dominatethegmat]

The GMAT exam is standard across all countries. I've had plenty of Canadian students sign up for my course and use their GMAT score to get into the top business schools in Canada (or U.S.). So yes, my course will be perfect for you in Canada. As for your weak math background, you sound like a lot of my students! That's the purpose of my course, to help you brush off your high school "math cobwebs" and relearn (or sometimes learn for the first time) certain math topics that are tested on the GMAT. As you've probably noticed, I try to teach things in ways that make them really to understand, so I think it'll be exactly what you need.

[@CharlesMata-o1t]

🤯THANKS !!

[@dominatethegmat]

My pleasure!

[@mariamonsegue8966]

Wow I just put them in cases and figure out how much I’m sharing works easier for me 😂 28 cases of 177 items etc I looked at the numbers and said ok it’s not 3 6 or 9 so it’s 4 cuz 1 doesn’t feel right 😩

[@dominatethegmat]

Haha, that's one way of going about it! Fortunately now you have a more systematic approach that will take the guesswork out of questions like this 😀.

[@rajen1211]

Hi brett Iam an engineering graduate there after worked as software engineer in a software company,and joined banking.presently i hav 2years software experience and 9years banking exp,suggest me whether to go for MS or MBA

[@dominatethegmat]

Hi Rajendra! Your work experience and education shouldn't dictate which degree you should go for, but rather your career aspirations and what you hope to accomplish with the degree. Get a clear picture of why you want to go to graduate/business school in the first place, and that will help determine which degree to go for and which schools to apply to.

[@ohkabomb917]

I get the reasoning but it appears i would need to review certain terms and reread the questions again and again to make sure i understand what was being asked lol. I initially thought that we needed to get the number of digits so i was bogged out of my mind ------ but then i realized that units digit meant the rightmost number so I solved it. Still, if this popped up in an actual test, i would've gotten it wrong since i didn't know what the hell was being asked in the first place or would've taken me ages to realize it lmao.

[@dominatethegmat]

That's part of the prep process. The GMAT asks the same types of questions over and over again and once you learn them all, you'll be able to recognize trigger words when a question pops up on test day. Now that you've seen this video, you know what a Units Digit is! If you put in the time to thoroughly prepare in an organized, systematic way, you'll know the terminology in all of the other types of questions, too, and there shouldn't be any surprises on test day.

[@asharsanavlogscanada5211]

Ong that makes so much of sense! Thanks for valuable teaching :)

[@dominatethegmat]

You're welcome. I'm glad this video helped you have breakthrough! Best of luck on the rest of your preparation and let me know how else I can help.

[@sharifullislamsharif6379]

Give me some list of books for GMAT exam

[@dominatethegmat]

Here are the books I like and use with my students in my own courses: www.dominatethegmat.com/gmat-online-practice-test/recommended-books-2/

[@vibhasharan6159]

Wonder of mathematics

[@dominatethegmat]

It's a beautiful thing, isn't it? 😀

[@tybaltbaptiste8899]

why was the unit in the 2nd power in 133 not 3, but in 177, the 2nd power was also 177?

[@dominatethegmat]

I'm not sure I fully understand your question. For 133, the units digit at the second power is whatever 3 times 3 is. For 177, the units digit at the second power is whatever the units digit of 7 times 7 is. By coincidence, they both happen to be 9. If the base numbers had been different (e.g. 176 and 133), then the units digits at the second power for each would not have been the same.

[@weikangchen6469]

That is exactly the same reasoning and first idea that came into my mind! lol

[@dominatethegmat]

Great minds, as they say...!

[@Sigmafacez381]

thanks interesting

[@dominatethegmat]

Glad you found it helpful!

[@ErwinAFrei]

Wow feel I have a long wat to go

[@dominatethegmat]

You might, but you'll get there one step at a time. Have you taken a full-length practice test yet?

[@shalushankar4460]

Greattttt. Superb sir

[@maryslens5330]

Thank you

[@dominatethegmat]

My pleasure!

[@goodvibess31]

at 11:28 can you please explain why you placed 1 on top of the 7. I just need better clarity please. Since the 7 is from 177^28 and 1 comes from 133^23 wouldn't it be 7-1 = 6?

[@dominatethegmat]

No, the 1 was the units digit for 177^28 and the 7 was the units digit for 133^23, so the ultimate different is ------1 - ------7. And then you can think through a simple version like 21 - 7 to realize that the units digit of that difference will be 4.

[@goodvibess31]

@@dominatethegmat It took me hours after writing this comment to finally realize how you had explained it in the video and also how we borrow from the tens to make it 11-7=4. Seriously, this is gold! Thank you!

[@dominatethegmat]

@@goodvibess31 Breakthrough! Your hard work will serve you well on test day.

[@faysalege]

Because its asking for the Units digit couldn't you take the 7 out of 177 and the 3 out of 133; and then subtract 7-3=4. Would that kind of reasoning not always work or is it flawed someway?

[@dominatethegmat]

It's flawed. The units digit of each number won't necessarily be 7 and 3, respectively, depending on how many times you're raising it to a certain power. So you actually have to do the initial multiplications like I did in this video and figure out the pattern. BUT, you do only have to focus on the 7 and 3 part.

[@Dayoolufotebi]

Dominate the GMAT can’t you recognize that both numbers will be odd no matter what and odd-odd=even eliminating three choices. And then if you take 177-133 you get 144 which has 4 in units place.

[@dominatethegmat]

@@Dayoolufotebi Your point about odds and evens is a good one. But then once you're choosing between the two even units digits answer choices, you can't just go with the original numbers. As I explained to Faysal, it's coincidence that the units digit of the answer happens to be the units digit of 177 - 133.

[@kakalikar9433]

Sir , why did u borrow from the tens column ? I didn't get that !

[@dominatethegmat]

Because you can't subtract 7 from 1 in the one's column. That's one of the tenants of long subtraction that to be able to subtract 7 from 1 in the one's column, you need to borrow from the tens column (and then reduce it by one, but we don't care about that part for this units digit question where only the units digit matters).

[@nonybrighto]

Just awesome!

[@dominatethegmat]

Thanks!

[@reniemathew3538]

This dude is fantastic!!

[@dominatethegmat]

Thanks, I appreciate that Renie!

[@unsung_tunes]

Cyclic method.reminder theorem

[@simonebuda9141]

Thank you thank you thank you

[@dominatethegmat]

You're welcome, Simone. Glad you found it helpful!

[@fsalgado98]

Your pronunciation is too perfect to be true

[@dominatethegmat]

I have a lot of students for whom English isn't their first language so I try to be as precise as possible. Glad you appreciate it!

[@pearlfreeman8727]

I know I am very late to this but what is the purpose for this weird way of reasoning when you are taught to get the answer? If I understand the math I should able to get the answer right?

[@dominatethegmat]

Do you have a simple "traditional math" way of solving this particular question? If you do, then go for it! I always tell my students that if you immediately "see" how to solve a problem the traditional way AND feel confident in your ability to execute the solution without making errors, go for it. But there are numerous benefits to learning alternative "reasoning" approaches to certain question types. First, some questions [like this one] can't be solved with a simple formula. They're meant to test your creative analytical abilities. The math portion of the GMAT is called Quantitative REASONING for a reason. Second, sometimes you get stuck on test day. You think you remember how to solve a question the way you were taught, but you can't quite get to a right answer. It's always helpful to have additional tools in your tool belt so that you can come at a question from a non-traditional way if necessary to still get a right answer.

[@zahraashari4331]

Ok, the thing is personally I'd go through the same path but as English is my second language I have no clue what "unit digit" stands for. So, I thought that it means how many digits is the answer and I was like have no f*ckin clue. The problem is I learnt mathematic phrases in other language. Is there any sources for people who English isn't their mother language?

[@dominatethegmat]

I totally understand, Zahra, and I hear that a lot from my students for whom English isn't their first language. Fortunately, I cover all of the terms and definitions you'll need in my comprehensive GMAT prep courses, which you can learn more about and register for here: www.dominatethegmat.com/video-purchase/. I'm looking forward to working with you!

[@zahraashari4331]

@@dominatethegmat Oh, that's great. Thanks.

[@mahedihasan1951]

Thank you so much #sir

[@jayneilmehta1778]

Just asking Can we not subtract 177-133= 44 28-23= 5 44*44*44*44*44= 164916224 Answer 4

[@dominatethegmat]

No, you can't combine exponents that way. Moreover, even if you could, you wouldn't have time to calculate 44x44x44x44x44 on your scratch paper without a calculator. That's the beauty of just focusing on the units digits!

[@Searcher626]

1 question: when you got the 2nd 7, how do you know it will always repeat after every 4? It is incomplete induction!

[@dominatethegmat]

Mathematically, is it ever possible to multiply 7 x 7 and have it NOT have 9 as the units digit? No, because 7 x 7 is ALWAYS 49. Then, is it ever possible to multiply 9 x 7 and have it NOT have 3 as the units digit? No, because 9 x 7 is ALWAYS 63. And then is it ever possible to multiply 3 x 7 and have it NOT have 1 as the units digit? No, please 3 x 7 is ALWAYS 21. And then is it ever possible to multiply 1 x 7 and have it NOT have 7 as the units digit? No, because 1 x 7 is ALWAYS 7. At this point, go back to my first question: 7 x 7 will always have 9 as the units digit, and then 9 x 7 will always have 3 as the units digit, and so on. The pattern clearly repeats itself after four 7's because the 1 x 7 puts us back at the beginning with 7 as the units digit. There's literally nothing else that can happen to interrupt that pattern since we're multiplying by 7 every time, which is the definition of what the exponent is telling us to do. Does that make sense?

[@amabdullaharrafiu9685]

ya after a certain time zero 0 starts to come at unit digit. I still want to learn.

[@vivekjoshi4058]

Well explained sir

[@amabdullaharrafiu9685]

The logic is very nice and very helpful also, but I think it actually does not work. I tried it to calculate in excel, unit digit comes 0 even very early.

[@dominatethegmat]

You might want to double-check something on your spreadsheet. It doesn't go to 0. The correct answer is 4.

[@RekhaSingh-sb3xl]

I can't understand,how 4came in the last, please define this

[@dominatethegmat]

Once you've determined that the units digit of the first term is 1 and the units digit of the second term is 7, then you can make an easier version to see how the difference will play out. Really everything before the units digits is irrelevant, so you can make up something arbitrary: e.g. what is 231 - 67? If you subtract those whether long-hand or on your calculator, the units digit will be 4. So it will be with whatever the terms really are.

[@rahult9283]

How did you know that it’s a pattern and that it won’t change midway? Btw the answer is right, I jus calculated it (using a pc of course)

[@dominatethegmat]

Good question. Generally in math when you have a repeating pattern (including a repeating decimal), it's going to continue repeating indefinitely. Here, the reason is that 7 x 7 will always end in 9. And then 9 x 7 will always end in 3. And then 3 x 7 will always end in 1. And then 1 x 7 will always end in 7. And because those are mathematical truths that will hold forever, once you get back to the number ending in 7, then when you multiply it by 7 again, it will always end in 9, and so on. The pattern literally repeats and it's impossible for anything to interrupt so long as you continue multiplying by 7 each time, which is what an exponent tells you to do.

[@anuinibuhnu9053]

@@dominatethegmat could this work? Because immediately you said the last digit is the units digit I took the 7 and the 3 from 133 and did the subtraction and had 4.

[@dominatethegmat]

@@anuinibuhnu9053 No, that's not something you can rely on working all the time. Eventually you will subtract the units digits of the two terms, but not before taking them to the 28th and 23rd powers, respectively. If either of those exponents were different, the end result would be different in most cases. For example, if the question were 177^27 - 133^23 instead, now the units digit of the first term would be 3 (not 1 anymore), the units digit of the second term would still be 7, and so now the end result would be a units digit of 6.

[@karinashaik218]

Y u have taken 11 at the end of the problem

[@dominatethegmat]

Because you can't subtract 7 from 1, so you have to borrow from the tens digit, changing the 1 to 11. Basically I'm just doing long subtraction without a calculator.

[@6flo]

I didn't understood the "powers" division

[@devamshah1090]

This was an easy question right

[@dominatethegmat]

It's not considered an easy question by GMAT standards, no. But if it was easy for you, that's great!

[@reemaxx2080]

Thnaks a million 🌷

[@dominatethegmat]

My pleasure, glad you found it helpful!

[@reemaxx2080]

Dominate the GMAT .. I did ☺️my exam is tmw🙃

[@stimulantdaimamld2099]

great

[@dominatethegmat]

Thank you!

[@varunb82]

I cud solve it precisely how you did it before watching the video...I think I must give gmat a go

[@dominatethegmat]

How did you do on your last full-length practice test?

[@varunb82]

@@dominatethegmat I have not given any practice test yet...

[@dominatethegmat]

@@varunb82 I'd highly recommend taking at least a couple before sitting for the real thing. There are two free ones on the mba.com website and I have 5 on my site here: www.dominatethegmat.com/gmat-online-practice-test/gmat-online-practice-test/

[@M1and5M]

And in the test there will be 2 min for that? :d

[@dominatethegmat]

That's right, you have approximately ~2:00 per question on the quant section. Now that you've seen this pattern and know how to attack it, you'll have no problem answering similar questions in under 2:00 on test day!

[@M1and5M]

@@dominatethegmat thanks for the info!

[@dominatethegmat]

@@M1and5M My pleasure!

[@walaaayman24]

waaaaaaaaaaaw perfect 😍

[@dominatethegmat]

Glad you liked it!

[@maguX09]

Great

[@dominatethegmat]

Thank you!