Bunuel wrote:

If d is a positive integer, is \(\sqrt{d}\) greater than 15?

(1) d is divisible by 25.

(2) d is divisible by 40.

Taking Numbers would help.

Statement 1: d is divisible by 25say d = 25; then d is divisible by 25, now \(\sqrt{25}\) = 5; it is less than 15

say d = 625; then d is divisible by 25, now \(\sqrt{625}\) = 25; it is greater than 15

Not sufficient.

Statement 1: d is divisible by 40say d = 40; then d is divisible by 40, now \(\sqrt{40}\) = 2 * roughly (3.5), it is certainly less than 15

say d = 400; then d is divisible by 40, now \(\sqrt{400}\) = 20; it is greater than 15

Not sufficient.

Combining Statement 1 and 2: d is divisible by 40 and 25 bothLeast value of such number would be 200 (LCM of 40 and 25).

say d = 200; then d is divisible by 40 and 25, now \(\sqrt{200}\) = 10 * 1.414, it is certainly less than 15

say d = 400; then d is divisible by 40 and 25, now \(\sqrt{400}\) = 20; it is greater than 15

Not sufficient.

Answer: E