Question

Which among the following is NOT a perfect square number?

• A. $49$
• B. $16$
• C. $-225$
• D. $169$

Answer 1

The correct option is C $-225$

$\bullet 49$ can be expressed as:
$49=7\times 7=7^2$
$\therefore 49$ is a perfect square number, and is a square of $7$.

$\bullet 16$ can be expressed as:
$16=4\times 4=4^2$
$\therefore 16$ is a perfect square number, and is a square of $4$.

$\bullet 169$ can be expressed as:
$169=13\times 13={13}^2$
$\therefore 169$ is a perfect square number, and is a square of $13$.

$\bullet -225$ cannot be expressed as:
$-225\ne (-15)\times (-15)$

Also, a negative number CANNOT be a perfect square. A perfect square numbers are always greater than or equal to $0$ as $0^2=0\times 0=0$.

$\therefore -225$ is NOT a perfect square number.

Therefore, option (c.) is the correct answer.