Estimating Square Root Of A Number


Step 1: Find the unit digit of square root from the unit digit of given number 

Step 2: Discard the last two digits and then check between which two squares the remaining numbers lie.


Unit digit of 256 = 6

Therefore, unit digit of square root = 4 or 6

Discarding 56, remaining digit is 2

1² < 2 < 2²

So 256 must be 14² or 16²

Since we know 15² is 225, we arrive at the solution square root of 256 is 16


Estimating cube root of a cube number

If the cube of 2 is 8, then 2 is said to be the cube root of 8.

If a large number is given and stated that it is a perfect cube then we can use the following method to calculate its cube root by the method of estimation.



Find the cube root of 729

alt interior angles alt interior angles