-
Mclaughlin
- Master | Next Rank: 500 Posts
- Posts: 131
- Joined: Mon May 05, 2008 10:46 am
- Thanked: 1 times
help me!
This topic has expert replies
Source: Beat The GMAT — Data Sufficiency |
-
parallel_chase
- Legendary Member
- Posts: 1153
- Joined: Wed Jun 20, 2007 6:21 am
- Thanked: 146 times
- Followed by:2 members
I think the answer is D.
ab^2=50, a (a^2 - b^2) = a^3 - ab^2
Statement I
a^3 = 8
8 - 50 = -42
Sufficient.
Statement II
ab=-10
ab^2=50
b=-5, a= 2
8-50= -42
Sufficient.
Hence Answer is D.
Whats the OA?
ab^2=50, a (a^2 - b^2) = a^3 - ab^2
Statement I
a^3 = 8
8 - 50 = -42
Sufficient.
Statement II
ab=-10
ab^2=50
b=-5, a= 2
8-50= -42
Sufficient.
Hence Answer is D.
Whats the OA?
-
Mclaughlin
- Master | Next Rank: 500 Posts
- Posts: 131
- Joined: Mon May 05, 2008 10:46 am
- Thanked: 1 times
-
Senator 153
- Senior | Next Rank: 100 Posts
- Posts: 35
- Joined: Mon Jun 09, 2008 3:05 am
- Thanked: 2 times
Since it's a data sufficiency question, we only need to figure out "a" and "b." In this specific question, we don't even need to simplify that equation in the stem.
(2) might strike people as "the complicated one." ab = -10 and we already know ab^2 = 50. Compare ab^2 and ab. ab^2 = (-5) ab. Set equal to zero: ab^2 + 5ab = 0 ==>> simplify into ab * (b + 5) = 0 and we already know that ab = -10, not zero. That leaves b = -5 as the only solution. a = +2. Since you've identified a & b, (2) is sufficient.
(2) might strike people as "the complicated one." ab = -10 and we already know ab^2 = 50. Compare ab^2 and ab. ab^2 = (-5) ab. Set equal to zero: ab^2 + 5ab = 0 ==>> simplify into ab * (b + 5) = 0 and we already know that ab = -10, not zero. That leaves b = -5 as the only solution. a = +2. Since you've identified a & b, (2) is sufficient.
