Question

The sum of all odd proper divisors of 360 is

• A. 77
• B. 78
• C. 81
• D. none of these

Answer 1

Answer: (B)

78

$360=2^3{3}^2{5}^1$
Sum of all the divisors $=(2^0+2^1+2^2+2^3)(3^0+3^1+3^2)(5^0+5^1)$
Sum of all odd divisors $=\left(2^0\right)(3^0+3^1+3^2)(5^0+5^1)$
$=78$