Cube root of ANY number in under 5 seconds Math Trick

This trick allows you to work out the cube root of any number fairly quickly, - and what's more it is easy to learn and remember!
You'll be doing vube roots in your hear - faster than a calcuator.
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[@sardius119]

Underrated channel

[@tonybarfridge4369]

For numbers which lie somewhat between cubes, the method becomes less accurate. IE ∛17, =2, +9/(2^2x3)= 9/12=3/4=.75, ans=2.75 actual answer 2.57. Using 3^3 gives 27-17=10, 10/(3^2x3)= 10/27= .37 [don't subtract from 3] (75+37)/2=56, ans= 2.56, much closer than 2.63 or 2.75. To get even closer or exact, subtract 2 from the 9, and add 2 to 10 in the 2nd case. This will produce 2.58 and 2.56 [by subtracting the .44 from 3], just either side of 2.57. So doing just one part would be only .01 off, which could be mentally adjusted. For 3 digit numbers use the same dual method or vary the differences by 5. In any case averaging the 2 results will achieve better accuracy.

[@dreamer178]

hello sir, i have a suggestion:- there are millions of indians who wants to learn quantitative aptitude subject (which many of them find it difficult to understand) for various competitive exams in india, since you are an expert in maths it would be of very helpful if you start making videos about that subject.

[@rylq8425]

ya exactly we all want this from him😀😀😀

[@joedi]

While I respect the channel, dude you should look up Vedic Maths by Bharathi Krishna Thirtha. In your own motherland lies a treasure!

[@Navneet07860]

Shhhh..!!🤫

[@nilupilu]

I love your accent and the way you teach and also the content. Thank you.

[@Flexatron86]

Love this channel!

[@nezumi.5015]

@tecmath Please pin this: For those concerned with 8:15 - See, if you put "6 -1/12" on a calculator, you will still get 5.92 (5.916666...). So, he has just simplified "-1/12" to "11/12". You can still do it either way, however. Enjoy!

[@LucySteyn-gq5bd]

0thank you so much this was super helpful ! ( your amazing

[@johnperkinson2394]

Thanks

[@MyMy-tv7fd]

nice

[@-JA-]

Thank you.👍

[@mathbalakabeer4657]

That's good, awesome

[@IS-py3dk]

Love it Sir 😁

[@ProWall43]

Thank you so much 👍

[@muffin7690]

Can you explain why you square the closest number and then multiply it by 3 please

[@xdxd-wn8kz]

Because is the cube lol, examples 3^3 is 3x3x3

[@fullmindstorm]

What a champ 👏🏼 thank you for this.

[@scmtuk3662]

What happens if we do this with a number we know is a cube number? For example, 343? The nearest cube number to 343 is obviously 343, which is 7³ so the first part of our answer is 7. Then we find the difference between our number and the nearest cube. In this case, it's 0. Then we take the 7, square it, and add 3 to get 7²+3 = 49 + 3 = 52. So, we have 7 + 0/52, which can then be simplified as ... 7. So, there you go. You've learned how to drive a taxi, by going from A to B, but then going past B, to get to C, then D, and then eventually going around the block to get back to B, because you're an idiot.... and then charge your passenger extra for the extra mileage.

[@saadhero9107]

Want to let you know that your channel is amazing and it helped me get much better at math. Thank you!

[@syphon5899]

How does the 8:15 part work? Could you make a video to elaborate on that?

[@nezumi.5015]

See, if you put "6 -1/12" on a calculator, you will still get 5.92 (5.916666...). So, he has just simplified "-1/12" to "11/12". You can still do it either way, however. Enjoy!

[@larrycho1260]

I have a question. From example 8:25, so if like in the case of 'Cubic of 33', in which the answer if positive "3(2/9)", then you just leave as it is. However if the answer is a negative like in the second case 'Cubic of 207', in which the answer is "6(-1/12)", you substract the answer to "6-(1/12)". I was wondering why that happened. Why the positive one "3(2/9)" does not being added and become "3+(2/9)" too? I know that this is already the right solution for shortcut, I'm just asking out of curiousity.

[@rosadidomenico6670]

Cube of 33 = 3,22222222..... ok?

[@JeeAspirantAIR1]

you add in both cases i.e 33^(1/3) is 3+(2/9) and in the case of 207^(1/3) it is added again and becomes 6+(-1/12) . And that is just6-(1/12)

[@tashiaraynor1528]

This may be a silly question, but would it work the same for any cube higher than the cube root of 10?

[@KKMaths777]

Mathematics 👉❤️💕💞

[@fliegeroh]

Fun

[@_ShahriarKabir]

What if a six or seven digit number comes like 1232356

[@venun4845]

😮

[@venun4845]

Nice

[@faranazsahar9255]

To confusing

[@rosadidomenico6670]

Yes is true

[@averydae1810]

was anyone as confused as I was with this explanation. 5 second explanation that takes 5 hours to understand.

[@mahendrakulhari1484]

😂

[@ThinkerOnTheBus]

2:37 "And, we can now put this as a decimal because one-eighth is equal to four point one two five." BZZZZZ!!!! Semantically incorrect. Always mean what you say; don't say what you mean!!! 1/8 =/= 4.125 1/8 = 0.125 The answer to the question at hand (What is the cube root of seventy?) is 4.125 . . . or at least approximately close to the cube root because like he states, this method for determining the cube root of any number will often only give an approximated value. The cube root of 70 is more like 4.1212852998085568193774891173664 . . . still only an approximate, but significantly closer to the true cube root of 70 than what 4.125 is. Perhaps you might view this as nit-picking, but when it comes to Mathematics, and the fact that many people can not perform the most basic of mathematical functions simply because they do not like mathematics, and they don't like it because they never had a decent grasp upon its concepts. A teacher who makes such semantical mistakes in their lectures, when explaining how to perform various calculations, the students may take the teacher quite literally, and they can not figure out how he had reached that answer, or how a formula exactly calculates some value, or any other various concepts. Sure, the more advanced students will see and recognize the teacher's error, and they can still see how the concept functions, and what the teacher had meant to say, so they will still learn the concept correctly, unless it is a totally new mathematical concept to them, then they might not catch the teacher's error, and in not catching it, they are at a loss in fitting everything together for some concept, and thereby, never come to understand said concept. Yet, many students will never recognize the teacher's mistake, and will only be left with hating mathematics even more than they had previously, leaving them only more confused when it comes to mathematics.

[@KKMaths777]

Nice

[@krishhhprj]

nice

[@Lulu_user3801]

This is great my only question is why are we going to the closest number to the actual number is it because u can get the accurate number only with calculator?

[@sukritijha7067]

Thank you so much I always found it difficult to estimate the cube root of a number in an answer!

[@johnryder1713]

Back to the good old times with Tecmath

[@brockormond4131]

So is this trick using the derivative to solve the cubed? (i.e derivative of x^3 is 3x^2) Do you do the same with other roots? (ex. x^5, use 5x^4, etc) Would it be more accurate is you continued using 2nd or 3rd derivatives? (i.e for x^3 it go to 3x^2 to 6x to 6)

[@baraatariqallahawyah670]

❤

[@kasmilaramselera4978]

This is great!

[@tecmath]

Thanks mate.

[@tanzistr]

Thankyou so much!!! It was a much needed video

[@coreymcdonald7745]

Can you a video on how to find perfect cube roots for 3 digits numbers??? Example, if I’m given the number 49,836,032, how can I easily calculate it so I know the cube root is 368, without a calculator? I can do 2 digit numbers easily, but not 3

[@tonybarfridge4369]

The cube root of 49 = 3~, the root of unit 2=8, so we have 3 _ 8 already. To get the middle digit is a bit tricky at first; We'll say a=8, 8^3=512, 836-512=324. The 2 is what to use in finding b the middle digit. 3a^2xb=?2, 192xb=?2, b can only be 6 (gives a unit 2 number) If you're like me it takes a while to get your head around it but it's worth it I feel.

[@coreymcdonald7745]

@UCObTVVqtaZFZwJ0coQvBT-w 3 cubed is 27 though… for the first digit.

[@tonybarfridge4369]

@@coreymcdonald7745 yes 3 because 4 is too high. The answer must be less than 400

[@coreymcdonald7745]

@@tonybarfridge4369 right. I knew that… 🙄🙄🙄🙄

[@tonybarfridge4369]

@@coreymcdonald7745 yes the first group is unlikely to have an exact cube root, but when the next root produces a higher result, we always choose the lesser and it works 🙂

[@ksmyth999]

I think it would be helpful for most people if you explained why this works. Actually you are calculating (n + alpha)^3 = target, using a known n and then solving for the first order of alpha.

[@censorthis152]

what an assanine and backwards way to arrive at something that's not even the accurate answer to something that serves no practical application outside the mere game that is math on an academic level.