DS Problem

[jitsy]

If a2 + b2 =13, what is the value of ab? (just to clarify, the 2s are squares)

(1) (a + b)2 = 25 (just to clarify, the 2 after a+b is square)

(2) a(ab3) = 108 (just to clarify, the 3 is cube)


Statement (1) ALONE is sufficient, but statement (2) ALONE is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) ALONE is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.



I got D since both can answer
But the test I took says the answer is A. Am I missing something? Doesn't B also help?

Please help.

[clock60]

if i got the typing well
a^2*b^3=108, 108=3^3*2^2, so possible values for a and b are
2^2*3^3=108 with a*b=2*3=6 and also
(-2)^2*(3)^3=108 with a*b=(-2)*(3)=-6
looks like 2 st insufficient

[jitsy]

My bad. Didn't consider the possibility of the negative 2 in the (B).

Thanks a lot. Appreciate it.

[anuptvm]

If a2 + b2 =13, what is the value of ab? (just to clarify, the 2s are squares)

(1) (a + b)2 = 25 (just to clarify, the 2 after a+b is square)

(2) a(ab3) = 108 (just to clarify, the 3 is cube)


Please help.

Statement 1 => a2 +2ab +b2 = 25 ; Given in the question that a2 +b2 =13 so we can find value of ab

Statement 2 => a2b3 = 2^2 . 3^3 which means a =2 ; b =3 OR a=-2 or b=3; so Stmt 2 insufficient

[frank1]

Yup i think A should be answer
as there is no way of cancelling square and cube powers (one will be always more)