Find the least number which must be added to the number 6412 to get a perfect square.

Correct option is D

Given:
The number is 6412.
Concept Used:
To find the least number that must be added, first calculate the square root of the given number, then round up to the next whole number. The square of this number minus the given number will give the least number to add.
Solution:
The approximate square root of 6412 is:
​$$\sqrt{6412} \approx 80.09$$​​
Rounding up, we take the next whole number, which is 81.
The square of 81:  $$81^2 = 6561$$​​
6561 - 6412 = 149
Therefore, the least number to be added is 149.