Question

The sum of positive divisors of $360$ that are not divisible by $3$ is

• A. 810
• B. 90
• C. 1167
• D. 630

Answer 1

Answer: (B)

$360=2^3\times 3^2\times 5^1$
$\therefore$ Sum of positive divisors of 360 that are not divisible by 3
= $(1+2^1+2^2+2^3)(1+5^1)$
= $(1+2+4+8)(6)=15\times 6=90$.