GMAT Ninja Quant Ep 12: Conversions & Rates I

[@emilyviolaaa]

Your whole GMAT series is helping me out so much ! Thank you ! I do get a little bit discouraged though as I rarely manage to solve questions within 2 minutes. It already takes me at least 30 seconds to understand and write down the fundamentals of the questions let alone calculate it thereafter (especially referring to questions like 9…)

[@GMATNinjaTutoring]

You're very welcome! We're so pleased you're finding the series helpful! Also, please, please, please don't worry about not being able to answer something like Q9 in under two minutes. We hoped that question would challenge EVERYONE who watched this video, even those people aiming for a Q50 or Q51. Most of our tutors would really struggle to solve that within two minutes, and you're doing well if you can even get to the answer to that one. I often find myself encouraging my students to take longer to read, understand, and write down the fundamentals of a question. Often, a big part of the challenge in a GMAT question is getting the first line of algebra written down. If you can get that right and you understand where you need to take that first line of algebra, you're in a great position to work through the rest of the problem efficiently and within a two-minute average. I hope that helps a bit and that you find the rest of the series as helpful as this video! Please keep us posted on how your studies go.

[@dhruvjoshi4861]

no one has ever simplified GMAT for me the way you guys have done. Thanks a lot.

[@GMATNinjaTutoring]

Thank you so much! ❤️❤️❤️

[@israfilisrafil908]

I always wait for ninja series. These episodes contain some sublime qualities.

[@GMATNinjaTutoring]

Thank you so much for the kind words, Israfil!

[@giorgiafontana6726]

Hello, thanks for the video! To me, QST 1 had a quicker solution ⤵ After calculating 10 miles = (1.6 • 10) = 16 km, I created a proportion (40 km : 1 hour = 16 km : x) and found that x = 2/5 hour. It's easy then to get to 24 mins by understanding that 1 hour/5 = 12(mins) and 12•2= 24 mins. Hope this can help someone out there :)

[@anmolchorgasti2103]

This video did a number on my confidence. I couldn't solve the last two questions as my entire approach itself was wrong. However, the explanations were fantastic. Thank you for uploading!

[@GMATNinjaTutoring]

Thank you so much for the kind words! And seriously, don't feel badly if you struggled on the last couple of questions -- these get TOUGH towards the end of the video. You can get your butt kicked by those, and still be in great shape for a wonderful quant score. Have fun studying, and thank you again!

[@into.peaces]

Bro sorry to say, but this video has the worst explanations for the questions. Can't really get through questions in comparison to other videos of the series.

[@ashishsinha9035]

Thanks GMAT Ninja and Branson for the excellent questions and explanations. The questions were real tough, though I was able to solve all on my own !

[@GMATNinjaTutoring]

Thank you so much for the kind words -- I'm glad that you got a good workout out of this. :) Have fun studying!

[@nathanduhlmeyer2778]

Regarding Q8, it is clear to me that (1) is sufficient. I just think that in regards to the question, it should be less than 1/30, so something like 29.99, and also less than 1,25, so ike 1,24. Which still answers the question, but I am just confused, why you would say that they produce at least 1/30 while it is said that a and b < 30. Or did I misunderstood something?

[@NewxToXThisxBiz]

funny enough, i put this into chatgpt and it said that statement 1 was not sufficient because it could be any number not 1/30 thus it was only suff when put together with statement 2. but when i said the correct answer was A: statement 1 suff but not statement 2. I think the reasoning is that when a

[@kimberlyng7287]

b1/30

[@mohitprabhat2449]

For Q8, when we combine the 2 stmts, wouldnt we solve by taking b=25.xxx (and not 30)?

[@varun110291]

I didn't understand the logic on 58:23 Why does it need to be 1/30 It doesn't mention anywhere that it needs to be this much. It simply says a less than b less than 30. So if a is 2, b can be 3. Can you please explain.

[@GMATNinjaTutoring]

Hi Varun! The rate of Chef Y does not need to be 1/30, but it does have to be AT LEAST 1/30. Because we're trying to determine whether we can make AT LEAST 60 pitas in one hour, we want to see what the minimum output of pitas would be, and that comes from looking at the minimum rate of pita production. So, we take a look at what the output would be if the rate of Chef Y is 1/30, and we know that Chef Y will produce at least 2 pitas in an hour. I hope that helps!

[@varun110291]

@@GMATNinjaTutoring Thank you so much GmatNinja. This really helps : )

[@TheEverburningFathom]

@@GMATNinjaTutoring My big confusion with this question is that the inequality does not show an "less than or equal to," so why is it valid for us to assume a value when it's not even an allowed value? In my work, I'm seeing the numbers are so darn close, that it's not something that can be hand-waved away

[@tudorsafta3742]

Q3 is a little unclear to me... if we know A + B = 7x/12min, why do we then divide x into this? You treat it as the rate, yet both A and B are already given in the desired format x/_mins. Thus, wouldn't 7x/12min be the work rate of A+B, leading to a ratio of 7/2, Answer E?

[@paulmoon7421]

58:03 why is the rate of chef x at least 1/1.25? also the rate of chef y at least 1/30? could you please explain?

[@surajpai6297]

Hey Paul, Let me try answering your question. 1.25 is the maximum since a is less than 1.25. So 1 / 1.25(max) is minimum. If a number can take a value with is its maximum then the reciprocal of value (1/max) would be its minimum.

[@srilanka739]

atleast 1/1/25 is from Statement 1 The slowest chef y can work is less than 30 - or you can say 29.999 - so just take 1/30 i.e. 2 pizzas every 60 minutes. in reality he can make pizzas a bit faster than this

[@quocanhnguyen4108]

Can somebody help to explain on question 6 that rate (r) need to be >1920? I thought the right to find is that r

[@flowmv]

Q.7, While pushing the question and coming to the conclusion that we need the Paul's rate only, won't we need the distance that Pete covered too? Because that's the distance Paul has yet to cover. So Paul's current rate * distance left (Pete's distance) would give us how long it would take for him to complete the track. Of course the answer would still be the same as we get the distance in both statements, but yeah. I'm not sure why the distance wasn't mentioned..

[@GMATNinjaTutoring]

The question asked how long "would it take Paul alone, running at his constant pace, to complete the marathon (26.2 miles)?" Notice that we're given a distance here -- 26.2 miles -- and asked to find out how long it would take Paul to run this distance. If you think of a Distance = Rate x Time formula, we're given the distance and asked to find the time. The only term left for us to work with in that formula is the rate. If we find the rate, we can answer the question. Since the distance is defined in the problem, we don't need to know anything about the distance Pete or Paul ran to answer the question. If we figured out that Paul ran at 5 miles per hour, it would take him 26.2/5 = 5.24 hours to run a full marathon "running at his constant pace". Alternatively, if we found out that Paul ran at 10 miles per hour, it would take him 26.2/10 = 2.62 hours to run a full marathon. As long as we can find the rate at which Paul runs, we can answer this question. I hope that helps!

[@parvindernogi6264]

Is the last question fair? How can someone solve that in 2 mins?

[@khoahoangcongdang9093]

Actually in question 5 we can see from (3t-5)(t+4) that t must be =5/3 (it can't be -4) so 100mins is correct (which is 5/3 hour)

[@ShravanKumar-py2mn]

For Question 6. I went the other way around. Calculated the 'distance' (bucket capacity) for both statements. Statement - 1 : capacity > (190 * 16 / 3) Question stem asks 'CAN' the bucket hold (192 * 16 / 3) gallons. Statement - 1 says it 'CAN' hold greater than (190 * 16 /3) Since the possibility of holding 192 * 16 / 3 gallons exists. It should be sufficient, no? Statement - 2 : capacity < (200 * 16 / 3) Similarly for statement - 2, CAN the bucket hold (192 * 16 / 3) gallons? Sure there is a possibility that it CAN hold. Hence sufficient, no? Am I reading too much into the 'CAN' part. We are not supposed to be 100% sure, even if there is a small possibility the answer should be yes. That's how I see it. Where am I going wrong?

[@pierof6837]

Hi, firstly thank u. For the Q8 about pitas, I follow a different logic that lead me to answer "D". We can write the formula: (rate x + rate y + rate z ) * 60 minutes must be >= 60 . So : 1/6 + 1/a + 1/b >=1. That formula in both case is respected. Where is my mistake?

[@wedyans8830]

My main problem is that, I'm not sure how to arrange the variables and put them the way you do. I find this kind of questions very challenging . Its like I have to make my own rule and answer it. this seems very hard. How to arrange the unknowns and make this simple for me. If you could help me with this please!

[@GRENinjaTutoring]

Thank you for this question! In general, a good place to start is to write down the equation Distance = Rate x Time, then see if you are given any specific information about the distance something traveled, its speed (i.e. rate), or the amount of time it took. From there, it's often helpful to define each piece of information with a distinct variable. Once you've done that, a chart can be helpful to put all this information in one place, especially if you are given more than one rate to deal with. And keep in mind -- if two machines are working simultaneously, you can add their rates. Please do let me know if that helps at all, or if there are any particular questions/parts of the video you'd like explained further!

[@MORICTRASH]

Does the last question even make sense? I mean regarding the math yes of course, but how can 2 ovens bake a pizza at the same time??? Like how can oven A and oven B "work together"? ahahahha

[@Alappavan]

Lol bruh 😂

[@guilhermejesusalves5119]

@@Alappavanthat shi was funny😂😂

[@rosarioastudillo4468]

Hello! I don't understand why in Q9 we can add rates. Isn't it suposed that the combined rate of the ovens, (1 / c), is equal to the sum of their independent rates, (1 / a) and (1 / b)? But in this video we are doing directly c = a + b.

[@GMATNinjaTutoring]

This all depends on what you define the variables a and b to be. It looks like you define a to be the amount of time it takes oven a to cook a certain number of pizzas. If we do that, then the rate of oven A is (1/a), and if we do the same thing for oven B, then we can add the rates by doing the sum (1/a) + (1/b). In the video, Bransen defines a to be the rate at which oven A cooks pizzas and b to be the rate at which oven B cooks pizzas. If we do this, then we can add the rates by doing the sum a + b. We're doing the same thing in both cases, but it looks different because we've defined a and b to be different things in each case. It doesn't matter which path you take, as long as you're clear about what you mean when you use the variables -- you should end up with the same answer, no matter which route you take. I hope that helps!

[@guille7497]

Thanks for the video Bransen. It's great. I don't know. I have the feeling that most questions you guys solve are ( or should be) obvious to most test takers who are around the 700s. I find that I struggle with most questions (I understand the answer you guys give without much effort but I mean, I struggle in my own attempts), specially since they should be solved in 2 minutes. I still have two weeks to prepare for the exam. Any suggestions? My plan is to do as many exercises as I can after completing the 19 quant episodes. In the meantime I try to learn patterns and techniques for the different kinds of problems , but I wonder if I simply can't get my target score of 670.

[@GMATNinjaTutoring]

I'm not sure if this helps at all, but quite a few of the questions in our videos are pretty tough. Sure, many of the questions cover just the very basics, but if your goal is something like a 700 on the "classic" GMAT, I certainly wouldn't expect you to nail all of them. If you can, that's awesome. But unless you're at the very very top of the score scale, it's fair to expect at least some pain as you work through the questions in these videos. Two weeks is an awfully tight timeline, and it's hard to give broad recommendations without knowing a whole lot more about what's going on. This video on how to use practice tests might help a little bit, though: kzbin.info/www/bejne/anTEXqBujK6pjsU. More broadly, I'd argue that you'll want to reserve plenty of time to do official practice questions and practice tests -- videos are nice, but high-quality practice is more important. Good luck with your studies!

[@PriyankaGupta-en6cq]

@@GMATNinjaTutoring Hey where can I find these practice test videos, please guide I'm kind of in a similar situation here, need to practice more.

[@tony8888able]

Q7. By any chance, do you have the results of how long took Paul and Pete to complete the marathon? I just feel like we need to verify if our assumptions using the info in both statements were right.

[@GMATNinjaTutoring]

We can calculate that from the information given in the question. As Bransen showed when looking at statement 1, we can calculate that Paul ran 5.24 miles in 2 hours. This means he ran at 2.62 miles per hour (not very speedy!) Given that a marathon is 26.2 miles per hour, it would take Paul 10 hours to run the marathon. We then know that Pete ran 20.96 miles in three hours from either the calculation above or the information given in statement 2, so we can calculate that Pete ran at 6.99 miles per hour. This means it would take him 3.75 hours to run the full 26.2 miles of the marathon. I hope that helps!

[@tony8888able]

@@GMATNinjaTutoring thanks so much!

[@komalpatil6160]

Hii... Could you guide if these quant series is actually helpful for the focused edition??

[@TheAmigoBoyz]

For Q6, does this in theory mean that if you ever get an inequality you know that it can never be C? There seems to be no possible way in which the two statements combined would ever reveal a useful answer that one of the two could not provide by itself

[@GMATNinjaTutoring]

It would be very risky to go into a question such as this assuming that the answer cannot be (C) because of the structure of the statements. While you may be correct, you run the risk of jumping to a conclusion and not considering the precise wording of that individual question. This leaves you open to the possibility of finding an exception to your "rule" and getting a question wrong that was well within your capabilities. It's much safer to consider the merits of each statement and each question individually to prevent any unnecessary slip-ups. I hope that helps!

[@TheAmigoBoyz]

@@GMATNinjaTutoringThanks, i agree -better safe than sorry

[@RahulKumarSinha2000]

29:12 Hello sir, in Q4, why we didn't wrote *-40(t+3/4)* instead of 40(t+3/4)? Since, the filling bucket sign is taken +ve, so according to that logic, the draining bucket should be of -ve sign. Please explain this.

[@GMATNinjaTutoring]

If we say that X is just the number of gallons in the bucket, then we don't need to change the sign when we fill or empty the bucket in this question. At 60 gallons per hour, we can say it takes t hours to fill the bucket so X = 1.5t. Similarly, at 40 gallons per hour, we can say it takes (t + 3/4) hours to empty the bucket so X = 50(t + 3/4). We could swap the words "fill" and "empty" in those two sentences and it wouldn't make any difference to the equations. This is because we've defined X as the number of gallons of water that the bucket holds without any reference to whether the bucket is being filled or emptied. I hpoe that helps!

[@RahulKumarSinha2000]

@@GMATNinjaTutoring Ok, thanks for clearing my doubt.

[@nujhatnoshinnijhu9170]

If the question is can it do or not like the gallon math ? Why even it is a problem that there are many probable values. Isn’t it a yes or no question ? Is value that important?

[@GMATNinjaTutoring]

I think you're asking about question 6, but please tell me if I'm mistaken. In this question, we know the hose fills half the bucket in 16 minutes, which would mean it could fill the whole bucket in 32 minutes. The calculation Bransen completes at the start of the solution shows that a hose pumping water at 1,920 oz/hr would fill an 8 gallon bucket in 32 minutes. This 1,920 oz/hr figure is the key to this question. If the hose was pumping water faster than 1,920 oz/hr then the bucket holds more than 8 gallons. And if the hose was pumping water slower than 1,920 oz/hr then the bucket holds less than 8 gallons. Statement (1) tells us that the hose is pumping water faster than 1,900 oz/hr. This means the hose could be pumping 1,901 oz/hr, which means the bucket holds less than 8 gallons as 1,901 oz/hr is slower than the 1,920 oz/hr figure we calculated earlier. It also means the hose could be pumping 1,950 oz/hr, which means the bucket holds more than 8 gallons. Since we can't tell from the information in statement (1) whether the hose is pumping water faster or slower than 1,920 oz/hr, this information is not sufficient for us to determine whether the bucket holds 8 gallons. This might be a yes or no question, but if the possible values for how quickly the hose is pumping water are either side of the key figure of 1,920 oz/hr then we can't answer this yes or no question. That's why the values are important. I hope that helps!

[@AnthonySamson-wl3gw]

Q3 - why would it be 2/7 and not 7/2?

[@GMATNinjaTutoring]

Hi Anthony! The idea is that because the time of a and b together is equal to w / r, the time of a and b together is equal to x / (7x/12). We then flip and multiply to find that t(a and b) = 12/7. The ratio of t(a and b) to t(c) would then be (12/7)/6 = 12 / 42 = 2 / 7. I hope that helps!

[@shirsendumaiti5682]

i did the same mistake. Question is asking the ratio of the time not the ratio of rates. It just another GMAt thing LMAO.

[@CarmenHorse]

i made the same mistake as well

[@epicbasel]

For Q9 can you explain how you know to set up the first algebraic equation as A and B equal to A+B. Vs for example setting y = (1/A) (T-5) and y = (1/B)(T) equal to each other because of Y. I did this trying to eliminate a variable and then later tried substituting in for 1/A to isolate T. When that algebra ended in mess I was already at 3 min.

[@GMATNinjaTutoring]

If I've interpreted your algebra correctly (and please tell me if I haven't!), your variable A stands for the amount of time it takes oven A to cook y pizzas. I think you'll find a rates question easier if you use the variable A to represent the rate of oven A. The reason for doing this is that you can add the rates, which is exactly what Bransen does as he sets up the first equation. We could consider a much simpler version of the problem to demonstrate this. Imagine you've got two machines, Machine A and Machine B. Machine A can produce 10 widgets per hour and Machine B can produce 20 widgets per hour. If we want to know how many widgets both machines working together could produce in an hour, all we'd have to do is add the rates together and we'd know they can produce 30 widgets per hour. In the question in the video, Bransen showed that the rate of oven A is y/(t + 5), the rate of oven B is y/t and the rate of both ovens working together is 3y/4. Since we know that we can add the rate of oven A to the rate of oven B to get the rate of them both working together, we can very quickly set up the equation: y/(t + 5) + y/t = 3y/4. I hope that helps!

[@MrDreamsofhell]

Is there a simple way to solve quadratic in last q8? I got stuck at that point

[@GMATNinjaTutoring]

Sadly, there isn't really a quick or easy way to solve quadratic like these -- they're just tough! The good news is that it's rare to see a quadratic like this on the GMAT, so you're in good shape if you were comfortable with the rest of the content in this video and only struggled with this quadratic at the end. If you'd like some more practice on solving quadratics where the leading coefficient is not 1, check out the Khan Academy link below. I hope that helps! www.khanacademy.org/math/get-ready-for-ap-calc/xa350bf684c056c5c:get-ready-for-limits-and-continuity/xa350bf684c056c5c:factoring-quadratics-by-grouping/a/factoring-quadratics-leading-coefficient-not-1

[@lorenzoolgiati2480]

Hi, I tried to solve question 5 with the weighted average between speeds but I got 7.33 m/s as result. I sure the procedure is right but I cannot understand why the results don't match, any idea?

[@GMATNinjaTutoring]

Hi there. I'm going to need a bit more information to know why the results don't match. If you lay out the path you took to arrive at 7.33 m/s, I'll take a look and see what I can find. Thank you!

[@meneerbart12a]

Suppose you split the 400m up in 4 sections of 100m, and the first section is ran 10 m/s and the last 3 are 'x'. The weighted average would be (10 + 3x)/4 = 8 m/s. Solve for x and you find x=7.33 m/s. However, the total time will then not match. 10m/s for 100m takes 10 seconds, 300m in 7.33 m/s takes 40.91 seconds, while running everything at 8 m/s takes 50 seconds. so you are running almost a second too long. You can't take the distance as weight but you should take the time as weight. Then you get (10 + 4x)/5= 8, solve for x and you get x=7.5m/s

[@vivianmburu5589]

am not understanding why we cant use same process in we used in statment one in statment 2 i cant understand why the we used the assumption in statement one for rate of chef b

[@GMATNinjaTutoring]

Hi Vivian! In statement one, we assume that the rate of Chef Y is at least 1/30 because it is written in the question that b < 30. This means that Chef Y makes at least two pitas per hour. We can make that assumption in statement two as well. But we don’t have much information about Chef X there. Sure, we can assume that the rate of Chef X is also a little bit more than two pitas per hour, but together, that makes only four pitas per hour. We may know that they make at least four pitas per hour, but we don’t know that they make at least 60 pitas per hour. So, statement two is insufficient.

[@shambhavikumar2338]

Hi, for question 8, how do you get that the rate of Y has to be at least 1/30?

[@GMATNinjaTutoring]

The question tells us that a < b < 30, so the greatest value b could take would be something slightly less than but very close to 30. This means that if we assume the greatest value b can take is 30 and the rate Chef Y can make pitas is 1/b, then the rate of Chef Y is at least 1/30. I hope that helps!

[@HaraChiaki]

@@GMATNinjaTutoring Hi, can you please provide more explanation for statement 2 on the same question? Why is it that it's insufficient... Thanks in advance!

[@CarmenHorse]

On Q 8, how did we get 1/30 for chef Y just because chef X is less than 1.25? The problem stated A is less than B which is less than 1/30, but how does statement 1 tell us chef Y is 1/30?

[@GMATNinjaTutoring]

Hi Joann, From the text of the question, we know b < 30, where b is the number of minutes it takes chef Y to make 1 pitta. If we try to find the rate that chef Y can make a pitta, we could use the W = R x T formula. If W = 1, so chef Y makes 1 pitta, and T < 30, since chef Y takes less than 30 minutes to make 1 pitta, then from W = R x T, we get 1 < R x 30 (the inequality sign comes from using T < 30 in this equation). This gives 1/30 < R, or if we put this in words: Y makes more than 1/30 pittas per minute. I hope that helps!

[@stefanierebers6448]

I do not understand how question 6’s answer is E. If I’m trying to determine if the rate of the house is >=1,920 ounces per hour then why isn’t statement 2 sufficient. If I know the rate is greater than 1,920 (2,000 ounces per hour), what else is needed?

[@stefanierebers6448]

Please disregard my question. Classic case of reading too quickly and thinking statement 2 said “more than 2,000” versus “less than 2,000”. Please carry on 😂

[@shirsendumaiti5682]

@@stefanierebers6448 XD

[@MohiQoziyeva-c1r]

Thank you

[@gianniniolu2218]

Is there a reason that in Q5 you didn't immediately solve for the time needed to avg 8m/s. Then solve for the time for the first quarter of the race, then subtract that time from the total time? This would leave you with 40s which you can then divide 300m by to get the answer?

[@GMATNinjaTutoring]

Hi Gianni! We wanted to show how you could work with the average speed formula in this question, but you're completely right that that's a viable (and potentially even more efficient) approach.

[@srilanka739]

@@GMATNinjaTutoring this is the method I used 400*1/4 = 100m at 10m/s therefore t = 10 seconds 40 seconds left to run 300m = 7.5

[@jeetratadia181]

Hi, I am still confused about question 6. Can you help me understand why the rate has to be greater than 8 gallons/ 32 minutes?

[@GMATNinjaTutoring]

We're told in the question stem that the hose filled half the bucket in 16 minutes. This means it would fill the entire bucket in 32 minutes. If the hose sprays water faster than 8 gallons per 32 minutes then the hose will have poured more than 8 gallons into the bucket by the time it's full. So if we determine whether the rate is greater or less than 8 gallons per 32 minutes, then we'll be able to tell whether the bucket holds more or less than 8 gallons. I hope that helps!

[@MouhibNourallah]

@@GMATNinjaTutoring one follow up to this question please. If we were told in statement 2 for example that the rate was exactly 2000 oz/hour then don't we know that more than 8 gallons was poured and so we know that it can hold 8 gallons which allows us to answer the question?

[@vergisvijaythomas6676]

@@GMATNinjaTutoring just to clarify your explanation after solving the question. If statement 2 said it poured less than 1910 gallons/hour , is it sufficient because we then would know that the bucket CANNOT hold 8 gallons? and if statement 1 said it poured in more than 1930 or 1950 gallons per hour, then we know that the Bucket CAN hold 8 gallons. Is my understanding correct?

[@lolritz9880]

probably a bad question but in question 9: are we equating 3y/2 pizzas to y pizzas & why? Thank you!

[@GMATNinjaTutoring]

Hi Lolritz! We definitely aren't equating 3y/2 pizzas to y pizzas. I can't tell quite where you got that from in the explanation, but maybe if you explain further, we'll be able to help. Let us know!

[@jimpadlocker9319]

The last question is very un GMAT like because the of the coefficients in the quadratic equation.

[@GMATNinjaTutoring]

Hi Jim! You’re definitely right that the last question is challenging, but quadratics with coefficients do show up on the GMAT. The last question is based on an official question with coefficients in a quadratic, and you can find it at the link here: gmatclub.com/forum/running-at-their-respective-constant-rates-machine-x-takes-2-days-98599.html Hope that’s helpful!

[@Conk-bepis]

I just use the unitary method which is pretty straight forward .....

[@niccolo_pace]

Sorry but I can't figure out why in Q8 the rate of chef B must be at least 1/30. In the question is written that b

[@GMATNinjaTutoring]

Hi Niccolò! You're correct that b

[@akshitsingh3752]

Hey Bransen first of all thank you so much for these GMAT quant and verbal series. I've a small doubt not related to any specific problem. In last question we ended up getting a quadratic equation. Do we ever need the quadratic formula to solve these equations or factorisation will work ?

[@GRENinjaTutoring]

Great question! In most cases, you'll be given quadratic equations that will be factorable. However, you may occasionally be presented with a quadratic equation that requires the quadratic formula to find the solutions. So while the quadratic formula isn't the most commonly tested topic, it couldn't hurt to know it. I hope that helps!

[@harshkhudania7587]

Nice prep but dude should just encircle correct answers at last of each question , just to be sure.

[@manjutripathi6146]

Hello, Thank You for the video, I have one doubt in question 5, could you please help me with that doubt. I have solved the question with this approach, Average speed of 4 quarters is 8m/s, sum of speeds of all four quarters= 8 X 4 = 32m/s. Speed in the first quarter =10m/s , hence sum of speed of last three quarters = 32-10=22m/s, hence average =22/3=7.33m/s , which is close to option c... Please guide me about the mistake in my approach. Thank you in advance.

[@GMATNinjaTutoring]

Hi Manju! It may be helpful to rewatch the explanation for that question because we touch on the approach that you used towards the end of our explanation in the video. But in short, the idea is that you can't treat average speed that way. Average speed is calculated by dividing the total distance by the total time. You can't simply take the average of two different speeds. For example, if I said that a car drove the first half of a trip at 60mph and the second half of a trip at 40mph, the average speed would NOT be 50mph. It would actually be 48mph because you spend more time driving at 40mph than you do driving at 60mph. The same concept applies to the logic that you used. I hope that helps! And let us know if you need further clarity!

[@stefanierebers6448]

I did the same thing as you at first. You likely tried to solve it using a weighted average approach, which you can BUT make sure it’s set up as a rate when you’re solving. Otherwise you’ll get 7.33 instead of 7.5.

[@danielgomes1631]

Q8 I didn't understand why Y = 1/30

[@GRENinjaTutoring]

We know that the amount of time required for Chef B to make a pita is less than 30 (a

[@purin586]

Kinda freaking out knowing ill prob fail my exam since i have no idea how to solve most of these questions. XD

[@mariokasel1429]

Bro I write on Wednesday, idk shit XD

[@purin586]

@@mariokasel1429 fk we r screwed

[@mariokasel1429]

@@purin586 nah we got this. I believe in u bro. Lets just hope no such thing as rates and ratios appear :D

[@purin586]

@@mariokasel1429 Let's just hope all the questions are 1 + 1 and all the reading is easy so we get 800 XD

[@mariokasel1429]

@@purin586 easy game 😂

[@parthnanavati6592]

Really didn't understand the logic behind 1/30 in question 8

[@GMATNinjaTutoring]

Hi Parth! The idea is that 1/30 represents 1 pita per 30 minutes. That equates to 2 pitas per 60 minutes. From there, we know that both Chefs X and Y produce at least 2 pitas per hour because the denominator in their rate will be smaller making their overall rate greater.

[@namanmanwani1131]

Sorry to say, it all started really clean and nice but through the video the explanation got ugly and very hard to understand, the worst explanation compared to other topics of the series.

[@ElectricGuitarStyles]

There's an easier way to solve 8 just by pure logic. Statement 1: a

[@GRENinjaTutoring]

Thanks for this comment! One thought about statement 1 -- if a < 1.25, does that mean that Chef X can make at least 5 pitas in 5 minutes? Not necessarily. Keep in mind -- there's no rule that Chef X can only make an integer number of pitas per minute. According to statement 1, Chef X can make more than 0.8 pitas per minute, but that doesn't necessarily mean Chef X can make 1 pita per minute.. For instance, Chef X could make 0.85, or 0.9 pitas per minute. Given all that, we'll want to combine the rates of all three chefs to be sure that statement 1 is sufficient. Thanks again for the comment, and let us know if that makes sense!