Is ab odd?
(1) a is even
(2) a is an integer
I can not see how to use statement (1). Experts, could you help me?
Is ab odd? (1) a is even (2) a is an integer
This topic has expert replies
-
- Moderator
- Posts: 426
- Joined: Tue Aug 22, 2017 8:48 pm
- Followed by:1 members
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
Target question: Is ab odd?ardz24 wrote:Is ab odd?
(1) a is even
(2) a is an integer
Since there's no information stating that b is an integer, we can jump straight to.....
Statements 1 and 2 combined
There are several values of a and b that satisfy BOTH statements. Here are two:
Case a: a = 2 and b = 1, in which case ab = (2)(1) = 2. So, ab is NOT odd
Case b: a = 2 and b = 1.5, in which case ab = (2)(1.5) = 3. So, ab IS odd
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
-
- GMAT Instructor
- Posts: 2630
- Joined: Wed Sep 12, 2012 3:32 pm
- Location: East Bay all the way
- Thanked: 625 times
- Followed by:119 members
- GMAT Score:780
If a is even, then a * b = even * b.
From there, if b is an integer, we must have even * integer = even, but if b is something else (√2, π, ½, whatever) we could have any result we like, be it even, odd, not an integer, not a repeating decimal, etc.
From there, if b is an integer, we must have even * integer = even, but if b is something else (√2, π, ½, whatever) we could have any result we like, be it even, odd, not an integer, not a repeating decimal, etc.
-
- Moderator
- Posts: 426
- Joined: Tue Aug 22, 2017 8:48 pm
- Followed by:1 members
Brent@GMATPrepNow wrote:Target question: Is ab odd?ardz24 wrote:Is ab odd?
(1) a is even
(2) a is an integer
Since there's no information stating that b is an integer, we can jump straight to.....
Statements 1 and 2 combined
There are several values of a and b that satisfy BOTH statements. Here are two:
Case a: a = 2 and b = 1, in which case ab = (2)(1) = 2. So, ab is NOT odd
Case b: a = 2 and b = 1.5, in which case ab = (2)(1.5) = 3. So, ab IS odd
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
Thanks Brent for showing such a great approach!!!