Question

Sum of all the odd divisors of 360 is :

• A. 70
• B. 78
• C. 80
• D. 88

Answer 1

Answer: (B)

$360=2^3\cdot 3^2\cdot 5$. Any odd divisor of 360 is of the form $3^a\cdot 5^b$
$\Rightarrow S=\left(3^0+3+3^2\right)\left(5^0+5^1\right)=78$