greater than

[Ankitaverma]

If d is a positive integer, is d^1/2 greater than 15?
(1) d is divisible by 25.
(2) d is divisible by 40.

Q/a -e

[Brent@GMATPrepNow]

If d is a positive integer, is d^(1/2) greater than 15?
(1) d is divisible by 25.
(2) d is divisible by 40.

Target question: Is d^(1/2) greater than 15?

If x > 0, then x^(1/2) = √x, so we can use this to rephrase the target question...
REPHRASED target question: Is √d > 15?

Also, since √225 = 15, √d will be greater than 15 only if d > 225
So, we can rephrase the target question as...
RE-REPHRASED target question: Is d > 225?

Okay, now let's jump straight to . . .

Statements 1 and 2 combined
We're looking for a number that is divisible by 25 AND is divisible by 40. There are several values of d satisfy these conditions. Here are two:
Case a: d = 200, in which case d < 225
Case b: d = 400, in which case d > 225
Since we cannot answer the RE-REPHRASED target question with certainty, the combined statements are NOT SUFFICIENT

Answer = E

Cheers,
Brent

[sanju09]

If d is a positive integer, is d^1/2 greater than 15?
(1) d is divisible by 25.
(2) d is divisible by 40.

Q/a -e

Or

Is d > 225?

(1) We have many 'divisible by 25' kinds of d, which may be less than 225 (e.g. 200), equal to 225, or even more than 225 (e.g. 250). Not sufficient. AD Gone BCE On.

(2) We have many 'divisible by 40' kinds of d, which may be less than 225 (e.g. 200), or more than 225 (e.g. 240). Not sufficient. B Ebbs CE Hangs About.

When taken together, we can have many a d divisible by both 25 and 40, starting from their LCM that is 200 (less than 225), 400 (more than 225), and countless ahead, but our purpose is met.

Answer is [spoiler]E[/spoiler].