Question

find the least number which must be subtracted from 3175 to make it perfect square​

Answer 1

$\huge\underbrace\red{Answer}$

39 is the Answer.

3175 - 39 = 3136 = 56^2.

See that the number 3175 is the square of a number 56.3…, and the largest integer below it is, you guessed it, 56. The Square of 56 is 3136. So your goal is to get to 3136, you start from 3175, you certainly have to go 39 lower.

You can use a calculator to find this, or use the long division method for square-root on paper, its really quite quick and easy. Also the square grid trick for finding squares is useful.