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Given: Q is a set of integers If Q contains more than 2 numbers,
To find: are all the numbers in Q even?

(1) The sum of any two numbers in Q is even.
Case 1: odd+odd = even
Case 2: even+even =even
Therefore the no. In set Q can be both ; all even or all odd.
(Insufficient)

(2) The product of any two numbers in Q is even
Case 1: odd*even = even
Case 2: even*even =even
Therefore the no. In set Q can be both ; all even or all even with one odd.
(Insufficient)

Combining both: Set Q have only one case satisfying both statements. That is Set Q have Even digits in set.
(Sufficient)
IMO C

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Bunuel
Q is a set of integers If Q contains more than 2 numbers, are all the numbers in Q even?

(1) The sum of any two numbers in Q is even.
(2) The product of any two numbers in Q is even.


Project DS Butler Data Sufficiency (DS3)


For DS butler Questions Click Here


Statement 1:
For a sum to be even, we need either odd+odd or even+even. We may have a case where all numbers are odd. Then if you pick any two odd numbers their sum would be even. We could also have the case where all numbers are even, so insufficient.

Statement 2:
For a product to be even, we need odd*even or even*even. It is possible to have one odd and the rest of the numbers in Q even, in that case any product is still even despite having one odd number. Thus it is possible to have one odd, or all even.

Combined:
Statement 1 has the cases all odd or all even. Statement 2 has the cases 1 odd or all even. Then combined we must have the all even case. Sufficient.

Ans: C
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Kindly see the attachment.
I was also tempted to mark B as the answer. Then I realized that for a product, 1 could be one of the elements.

IMO C
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1.jpeg [ 84.57 KiB | Viewed 1971 times ]

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