Bunuel wrote:

Is the positive integer p a multiple of 50?

(1) p is a multiple of 10

(2) p is a multiple of 5

Required: Is p a multiple of 50?

Statement 1: p is a multiple of 10

P can be 10, 20, 30, 50, 100 etc.

Therefore p may or may not be a multiple of 50

INSUFFICIENT

Statement 2: p is a multiple of 5

P can be 5, 10, 15, 50, 55 etc.

Therefore p may or may not be a multiple of 50

INSUFFICIENT

Combining Statement 1 and Statement 2:

P is a multiple of 10 and 5 both

Still p can have values such as 10, 20 , 30, 50, 100

Therefore p may or may not be a multiple of 50

INSUFFICIENT

Option E