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.

Example:

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.

Example:

 

Find the cube root of 729

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