Question

Find the least number which must be subtracted from the following number so as to get a perfect square.
$4000$

• A. $86$
• B. $27$
• C. $63$
• D. $31$

Answer 1

Answer: (D)

$31$

Here $123\times 3=369$ is less than $400$
$124\times 4=496$ is more than $400$
Hence, the required difference $=$ $400-369=31$
$4000-31=3969$ is a perfect square.

And $\sqrt{3969}=63$