HomeНаука и техникаRelated VideosMore From: MindYourDecisions

How To Calculate Cube Roots In Your Head

160994 ratings | 6414917 views
Here's how you do cube roots in your head! Avoid looking like Education Secretary Nicky Morgan who was stumped when asked to do a cube root: https://www.youtube.com/watch?v=x8CV0dfQMdU Note: the starting number needs to be a perfect cube. So it's more of a magic trick: ask someone to cube a number and then you can deduce their original number quickly. Check out my book "The Best Mental Math Tricks" (rated 4.7/5 stars on 4 reviews) http://amzn.to/18maAdo Can you multiply 97 by 96 in your head? Or can you figure out the day of the week when you are given a date? This book is a collection of methods that will help you solve math problems in your head and make you look like a genius. "The Best Mental Math Tricks" (rated 4.7/5 stars on 4 reviews) http://amzn.to/18maAdo H/T Mashable http://mashable.com/2014/12/12/education-minister-maths-question/ Arthur Benjamin is a Professor at Harvey Mudd College and well-known for feats of mental calculation. He explains the cube root algorithm in this pdf https://www.math.hmc.edu/~benjamin/papers/Cubing.pdf This trick is really old--here's a newspaper article from 1913 that explains the trick! http://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=SFC19130615.2.162.13.11 Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Playlist to watch all videos on MindYourDecisions https://www.youtube.com/playlist?list=UUHnj59g7jezwTy5GeL8EA_g This is the only channel to feature math topics suggested by people around the world. Support the channel on Patreon so we can share the beauty of mathematics and make the world a better place: https://www.patreon.com/mindyourdecisions If you buy from the links below I may receive a commission for sales. This has no effect on the price for you. My Books "The Joy of Game Theory" shows how you can use math to out-think your competition. (rated 4/5 stars on 34 reviews) http://amzn.to/1uQvA20 "The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" is a handbook that explains the many ways we are biased about decision-making and offers techniques to make smart decisions. (rated 4.6/5 stars on 3 reviews) http://amzn.to/1o3FaAg "Math Puzzles Volume 1" features classic brain teasers and riddles with complete solutions for problems in counting, geometry, probability, and game theory. Volume 1 is rated 4.4/5 stars on 13 reviews. http://amzn.to/1GhUUSH "Math Puzzles Volume 2" is a sequel book with more great problems. (rated 4.5/5 stars on 6 reviews) http://amzn.to/1NKbyCs "Math Puzzles Volume 3" is the third in the series. (rated 4/5 stars on 6 reviews) http://amzn.to/1NKbGlp "40 Paradoxes in Logic, Probability, and Game Theory" contains thought-provoking and counter-intuitive results. (rated 4.4/5 stars on 13 reviews) http://amzn.to/1LOCI4U "The Best Mental Math Tricks" teaches how you can look like a math genius by solving problems in your head (rated 4.8/5 stars on 5 reviews) http://amzn.to/18maAdo "Multiply Numbers By Drawing Lines" This book is a reference guide for my video that has over 1 million views on a geometric method to multiply numbers. (rated 4.4/5 stars on 5 reviews) http://amzn.to/XRm7M4 Connect with me My Blog: https://mindyourdecisions.com/blog/ Twitter: https://twitter.com/preshtalwalkar Facebook: https://www.facebook.com/pages/Mind-Your-Decisions/168446714965 Google+: https://plus.google.com/108336608566588374147/posts Pinterest: https://www.pinterest.com/preshtalwalkar/ Tumblr: https://preshtalwalkar.tumblr.com/ Instagram: https://instagram.com/preshtalwalkar/ Patreon: https://www.patreon.com/mindyourdecisions Newsletter (sent only for big news, like a new book release): http://eepurl.com/KvS0r
Html code for embedding videos on your blog
Text Comments (4901)
Parth Thakrar (23 hours ago)
U are wrong cube root of31004 is not 34. U have chosen the numbers which satisfy your rule
Child Violater (1 day ago)
Ok but what if we take 1 out of 39304 we would get 39303 but the answer of the cube would be bigger...
manish kumawat (1 day ago)
From your trick cube root in 636056, 636 is more closer to 729. so cube root is 96 which is wrong ans. Please explain
DJ (1 day ago)
0:02 - he lost me there
ravathu jahnavi (1 day ago)
In the second example, you took the number 636,056. The number 636 is actually closer to 729. This is because 636 - 512 = 124. Where as 729 - 636 = 93. So according to your expanation, the answer must be 96 right? And even in the third case, 185 is actually nearer to 216 than 125. So I think you must mention something like this - '' YOU CHOOSE A CUBE NUMBER WHICH IS CLOSER AND AS WELL AS SMALLER THAN THE NUMBER YOU HAVE. FOR EXAMPLE, IF WE CONSIDER 185,193 , ''125'' IS CLOSER AND SMALLER THAN 185. ''
divyesh Vegad (2 days ago)
Where is math proof man ?
David Pike (2 days ago)
You need to be clearer. Not a good explanation. 6/10
Uthaya Kumar (2 days ago)
What is about
Life Is Awesome (2 days ago)
Lol...we have this formula in our Indian vedic math!
Ghost Driver (2 days ago)
Thx
Renzo Lumibao (2 days ago)
He just use examples that will execute the true answers but when you use other examples some will not get the right answer
Renzo Lumibao (2 days ago)
This is not true
Aasiyah Tanveer (2 days ago)
Very useful...helped me a lot....thxx fr uploading this video
indra ippg (2 days ago)
Hats off Bro
Hakalabakala (2 days ago)
1:15 187 mathebande
Partho Sarkar (2 days ago)
Try 43804....ans is also 34....wrong method
William Guenthner (2 days ago)
This is absolutely useless.
Rajesh Dwivedi (2 days ago)
thanks brother
Nautilist (3 days ago)
Awsme approach👌
Rajat's Stuff (3 days ago)
What if in case of decimals
Sangeetha Ps (3 days ago)
Good thank you
mickey fisher (3 days ago)
This dont work
Oliver Christensen (3 days ago)
tecmath?
Shubh Labh (3 days ago)
How is 185 closer to 125 and not 216?
KENJI (3 days ago)
well it isn't exactly the closest one, but the closest one that's smaller, so: 185 --> 125 (5^3) 215 --> 125 (5^3) 216 --> 216 (6^3) (copied from my other comment btw)
Smart Arfaan (3 days ago)
Wow seriously? She wasn't able to say the cube root of 125? Did she even go to school?
Fainted (3 days ago)
Why am I watching this? I don't even know what a cube root is!
Goopi Beast (3 days ago)
I swear if this fails on my test
MinePro 3004 (3 days ago)
I have liked and subscribed!
MinePro 3004 (3 days ago)
thx for the tips!
Prince Panchal (3 days ago)
_____ *THIS VIDEO TITLE* How To Calculate Cube Roots In Your (Head) Its not~head~its mind
Kousei X Fairytail (4 days ago)
This was actually easy. Just gotta memorize
William Ryan (4 days ago)
What do you mean by ‘closest cube w/o going over’? Going over what? You seemingly go past the cubes used in the answers. Thank you.
William Ryan (4 days ago)
Do you mean the closest cube that is less than the number in question?
Menna Khattab (4 days ago)
What about a no. Smaller than a thousand , how am I to ignore the last three no.
Praveen Tyagi (4 days ago)
It is gud but what will happen if it is not perfect cube???
Marcus Mitchell (4 days ago)
This only works when the cube root is an integer. Please say that.
rohan shetty (4 days ago)
How is 185 closest to cube of 5 which 125 and not cube of 6 which is 216??
KENJI (3 days ago)
well it isn't exactly the closest one, but the closest one that's smaller, so: 185 --> 125 (5^3) 215 --> 125 (5^3) 216 --> 216 (6^3)
Bryan Penny (5 days ago)
This works well when the cube root is a 2 digit number it does not seem to work when the cube root is a 3 digit number.
Alla Hassan (5 days ago)
Is this rule apply for more than 7or 8 digits number? I really haven’t try yet I just watched the video. Thank you
ömer kaynak (5 days ago)
türkçe altyazı olsa daha iyi olur
Betim Mustafa (5 days ago)
#1 *Get a head*
Gabby's OMG Vids (5 days ago)
I'm still confused.
The tinkering Tox (5 days ago)
How do you do bigger numbers? I dont understand this completely and I want to know
Bob bob Bo (5 days ago)
This is funny how the thumbnail is incorrect
Hugo Abe (5 days ago)
This is useful for math olympic, Thank you
July M. (6 days ago)
34 is not the square root of 39,304
The Jello wolf (6 days ago)
Why am I watching this, why?
The Smiths (6 days ago)
"Why is this useful?" Proceeds to not explain why useful... because it's not.
Hope Rules (6 days ago)
You make me miss math class!! Thanks for sharing!!
Hudi Singh (7 days ago)
gud
Kartikeya Sharma (7 days ago)
Loved it
Ezat rashid (7 days ago)
is it the same with square roots???
Jacob Gechtman (7 days ago)
It doesn't work for 23^3=12167...
Ayushi Sharma (8 days ago)
method is easy but it has some limitations.. difficult to find out exact cube roots of imperfect cubes and decimal numbers with this trick....#MindYourDecisions pls make some trick for decimal and imperfect cube numbers..
SuperNova 5000 (8 days ago)
So it have to be a perfect cube root number?
thokchom Abung (8 days ago)
Sir any point lies in no. How calculate
ill - vent (8 days ago)
185 is closer to 216 not 125, the answer is then 67.
FGV Cosmic (8 days ago)
To everybody in the comment section THIS ONLY WORKS FOR PERFECT CUBES.
Peiwen Lin (8 days ago)
i will try to memorize as long as i can, but thanks
Kosiarz (8 days ago)
Czy tylko mi jakimś cudem tytuł wyświetlił się po polsku? Pierwszy raz się spotykam aby tłumaczono tytuły filmów na inny język na yt.
Vishnu Chinni (8 days ago)
4:12 u said its closest to 5 without going over but it is going over
Milana Lyv (8 days ago)
or just as simply as that, use a calculator.
Owen Benson (9 days ago)
185 is closer to 6 not 5??
Tricia Kading (9 days ago)
Doesn’t work for 89
Ali Rida Bahja (9 days ago)
I gave up memorizing since school
Zhexi Zhexi Chen (9 days ago)
But this method it doesn´t work with numbers lower of three digits, because it says "ignore" the last three digits. So how can I do it?
Kirokill (9 days ago)
My thanks
Husserl North (9 days ago)
cool
BackflipsBen (9 days ago)
0:37 "The cube of a number is the number multiplied by itself three times." WRONG! The cube of a number is the number multiplied by itself two times.
BackflipsBen (2 days ago)
+Lie Jam I get the confusion. It's all good, you're not the one who called me a retard haha
BackflipsBen (2 days ago)
+kils meh OK retard let me make it easy for you A number multiplied by itself once 5x5 = 25, that's a square A number multiplied by itself twice 5x5x5 = 125 that's a cube A number multiplied by itself three times 5x5x5x5 = 625 that's 4th power
Lie Jam (2 days ago)
Oh, yeah. This confused me. A cubed is when you multiply itself twice. It's just in the third power, my bad.
Lie Jam (2 days ago)
+BackflipsBen 5^2 = 25 5^3 = 125
BackflipsBen (2 days ago)
+Lie Jam 5 multiplied by itself once is 25. 5 multiplied by itself twice is 125. You tell me which is the square and the cube.
black (10 days ago)
Short and nice
Savitha Vj (10 days ago)
Wow really it is very easy
Cameron Lambert (10 days ago)
Cool trick!
Query Azerty (10 days ago)
It doesn’t work with 35
Joshua Lyttle (10 days ago)
is it closer to the nine one than the 8
Adem Kouki (10 days ago)
Or just use a calculator...
P d (10 days ago)
Six digits can easily be find out by separating 3 digits at a time ..right? Based on trick
Sleep Cube (10 days ago)
I hate this video with all my heart. It's tricks like these that make the world stupider. This works for small perfect cubes. I'm reporting this as false and misleading.
BobsAndVegane (10 days ago)
Great, now I'll finally be able to figure out the cubed root of 8. Damn, I have to memorize it.
Marcus Gramling (10 days ago)
Thumbnails fake, I checked it in my calculator.
Yung Chubbz (10 days ago)
You made me feel smart at 3:40 AM. #Kudos!
Nader Nad (11 days ago)
How about if got number 16654477 ?
Jacob Zandy (11 days ago)
88 doesn’t work either
Priya (11 days ago)
Woww. I will use this trick in my exam. Thanks
Miguel Hernandez (12 days ago)
What's the square root of give me my house back?
Хири Кири (12 days ago)
Интерестно)))(лишь бы российский стиль бы был)
Dark Phoenix (12 days ago)
The great thing about your channel apart from showing how cool, fun and fascinating math is, is that millions of people take a genuine interest in this subject as well. I think that bodes well for the future of humanity because math is essential to the STEM fields and ofc scientists and engineers are needed to advance technology and human civilization.
Soumya Jain (12 days ago)
thanks for giving me such a useful piece of knowledge, keep making more such videos
Ken lei (12 days ago)
I try this method with any numbers but it doesnt seem to work :/
Louden Moran (12 days ago)
What if the number has more than 6 digits
Samuel Sanda (12 days ago)
WUT?
Girish Thakur (12 days ago)
185 is more closer to 216 and not 125, your theory doesnt work here.
The cube rout of 912673 should be 93 but the real cube route is 97? how??
pro. peradox (12 days ago)
Vedic mathematics. Indian
haseeb ahmed (12 days ago)
Wrong, trick failed by you. In 2nd Example the number 636 is closer to the cube of 9 not 8, here your trick fails. So, its not the universal trick for finding cube root of any number. You just chose the ideal numbers for solving Examples.
Arne Brod (10 days ago)
no the rule is u cant go over, so 8 is the closest not over
Bob Jones (13 days ago)
Why would anyone need to calculate cube root in their head? Like EVER!
All with SARVESH (13 days ago)
It's easy to learn till 10 and I have
Praneeth Kumar (14 days ago)
What if the number is not a proper cube
Mohan Gowtham (15 days ago)
185 is closer to 215 than 125 then y did u choose 125
Mohan Gowtham (13 days ago)
+MRJAY thank u so much I missed it
MRJAY (13 days ago)
Mohan Gowtham because he said “WITHOUT GOING OVER” 216 is clearly over 185
Hydrate Plays (15 days ago)
If you can't memorize numbers but can memorize the lyrics of Fefe by SixNine, shame on you
Vijay Singh (16 days ago)
What about cube root of 195,112. Which is 58. But solving by same technic its not coming.
Daniel K. (14 days ago)
Vijay Singh Na, it actually does work out :) The last number of 195.122 is "2" and as said in the video 2 & 8 and 3 & 7 are to be switched places to get the first digit.. Hence you get the first number "8". Then you provide to erasing the last three digits after which you get 195. 195 is (without going over) closest to 125 which leads to "5" as our second digit --> cube root 58
Parallaxus (16 days ago)
Saying "without going over" is incorrect. Part of learning higher math is having a good grasp of language.

Would you like to comment?

Join YouTube for a free account, or sign in if you are already a member.