Math Is Fun Forum

dineshhx

Member

Registered: 2015-01-09

Posts: 1

How to Calculate Cube Root of a Number in 10 Seconds

The first and the most important step is to memorize the cubes of 1 to 9. These would form an important part of your toolkit in solving the cube roots. Here is a table for your convenience.

1 –> 1
2 –> 8
3 –> 27
4 –> 64
5 –> 125
6 –> 216
7 –> 343
8 –> 512
9 –> 729

Once you memorize this list, the next step is to remember the last digit (unit digit) of each of these cubes. Here is the list again, only with unit digits this time.

1 –> 1
2 –> 8
3 –> 7
4 –> 4
5 –> 5
6 –> 6
7 –> 3
8 –> 2
9 –> 9

That’s it. Now that you have memorized the cubes of first 9 natural numbers and their unit digits, you are all set to amaze your friends by calculating cube roots within 5 seconds (given that they have not read this article).

Calculate the cube root of 941192.
Step 1 ->  We get two parts i.e. 941 and 192.
Step 2 ->  The largest cube less than 941 is 729 (cube of 9). So, ten’s digit is 9.
Step 3 ->  The ending digit is 2. Hence, unit’s digit is 8. That’s it. 98 is the answer.

Practice it a bit and you would be able to solve this in even less than 5 seconds.

You can verify your answer at Easycalculation.com

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: How to Calculate Cube Root of a Number in 10 Seconds

hi dineshhx

Welcome to the forum.

Interesting post.  Thanks,

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Stangerzv

Member

Registered: 2012-01-30

Posts: 266

Re: How to Calculate Cube Root of a Number in 10 Seconds

I can do it even faster:) With a calculator!