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Is ab odd? (1) a is even (2) a is an integer

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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Thu Oct 12, 2017 6:38 am
ardz24 wrote:Is ab odd?

(1) a is even
(2) a is an integer
Target question: Is ab odd?
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

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Brent
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by Matt@VeritasPrep » Fri Oct 13, 2017 11:44 am
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.
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by BTGmoderatorAT » Sat Oct 14, 2017 7:09 am
Brent@GMATPrepNow wrote:
ardz24 wrote:Is ab odd?

(1) a is even
(2) a is an integer
Target question: Is ab odd?
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!!! :D
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