Trick to Find Cube Root of a number without Calculator

Trick to Find Cube Root of a number without Calculator

Cube Root.Number
CubeLast Digit of Cube
0 0 0
1 1 1
2 8 8
3 27 7
4 64 4
5 125 5
6 216 6
7 343 3
8 512 2
9 729 9
Trick Used:
We will follow these steps to find the cube root of a number:
1.Ignore the last3 digitsof the number. Let remaining number be“I”.
2.From the above table check which number’s cube is less than or equal to‘I’. It will be left part of our answer. Let it be“L”.
3.Let Right part of our answer be“R”. It will be determined from the above table. For Ex. If last digit of question is7, then last digit of our answer will be3.
4.Our answer will beL|R.

Example 1
Suppose we want to find the cube root of21952.
Step 1:Ignore last three digits of 21952. Remaining number left is’21′.
Step 2:From the above table cube of’2′is less than’21′. Therefore left part(L)of our answer will be’2′.
Step 3:Since last digit of‘21952‘is‘2‘. Therefore right part(R)of our answer will be’8′. (Because Last digit of ‘cube of 8′ is 2. see table above.)
Step 4:Our Answer will beL|R. Therefore Answer will be 2|8 =28.
Example 2
Suppose we want to find the cube root of148877.
Step 1:Ignore last three digits of 148877. Remaining number left is’148′.
Step 2:From the above table cube of’5′is less than’148′. Therefore left part(L)of our answer will be’5′.
Step 3:Since last digit of‘148877‘is‘7‘. Therefore right part(R)of our answer will be’3′. (Because Last digit of ‘cube of 3′ is 7. see table above.)
Step 4:Our Answer will beL|R. Therefore Answer will be 5|3 =53.
Example 3
Suppose we want to find the cube root of636056.
Step 1:Ignore last three digits of 636056. Remaining number left is’636′.
Step 2:From the above table cube of’8′is less than’636′. Therefore left part(L)of our answer will be’8′.
Step 3:Since last digit of‘636056‘is‘6‘. Therefore right part(R)of our answer will be’6′. (Because Last digit of ‘cube of 6′ is 6. see table above.)
Step 4:Our Answer will beL|R. Therefore Answer will be 8|6 =86.