Question

Find the least perfect square that is exactly divisible by 4, 5, 6, 15, and 18.

• A. $100$
• B. $256$
• C. $400$
• D. $900$

Answer 1

The correct option is D $900$

LCM of $4,5,6,15,and18$
$4=2\times 2$
$5=5\times 1$
$6=2\times 3$
$15=3\times 5$
$18=2\times 3\times 3$
So, L.C.M=$2^2\times 3^2\times 5=180$
$180$ when multiplied by $5$ becomes a perfect square.
$\therefore$ Required number=$180\times 5=900$