Odd even

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Odd even

by sud21 » Sat Sep 19, 2015 5:53 am
Is ab odd?
1. a is even
2. a is an integer

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by [email protected] » Sat Sep 19, 2015 11:11 am
Hi sud21,

This question can be solved by TESTing VALUES.

We're asked if (A)(B) is odd. This is a YES/NO question.

1) A is EVEN

IF....
A = 2
B = 1
(A)(B) = 2 and the answer to the question is NO.

IF....
A = 2
B = 1/2
(A)(B) = 1 and the answer to the question is YES.
Fact 1 is INSUFFICIENT

2) A is an INTEGER

The same two TESTS that we used in Fact 1 can be used here:

IF....
A = 2
B = 1
(A)(B) = 2 and the answer to the question is NO.

IF....
A = 2
B = 1/2
(A)(B) = 1 and the answer to the question is YES.
Fact 2 is INSUFFICIENT

Combined, we already have two different results that fit BOTH Facts.
Combined, INSUFFICIENT

Final Answer: E

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by Matt@VeritasPrep » Fri Sep 25, 2015 11:06 am
S1::

If a = 2 and b = 3, no
If a = 2 and b = (1/2), yes

NOT SUFFICIENT

S2::

We don't know anything about a and b's values.

S1 + S2::

We STILL don't know about b! So we can't solve, unfortunately.

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by Brent@GMATPrepNow » Fri Sep 25, 2015 11:30 am
sud21 wrote:Is ab odd?
1. a is even
2. a is an integer
Notice that statement 2 does not add ANY EXTRA information beyond the information that statement 1 provides.
So, if statement 1 is insufficient, then statement 2 must also be insufficient, and the COMBINED statements are insufficient.

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by Matt@VeritasPrep » Fri Sep 25, 2015 11:33 am
Brent@GMATPrepNow wrote:
sud21 wrote:Is ab odd?
1. a is even
2. a is an integer
Notice that statement 2 does not add ANY EXTRA information beyond the information that statement 1 provides.
So, if statement 1 is insufficient, then statement 2 must also be insufficient, and the COMBINED statements are insufficient.

Cheers,
Brent
Now that is an excellent point, and one that will apply to lots of other DS questions too.