BTGmoderatorDC wrote:Is (xy - y) even?
(1) x and y are consecutive numbers.
(2) y is odd
OA C
Source: e-GMAT
So, we have to determine whether (xy - y) even.
(xy - y) = y(x - 1)
Let's take each statement one by one.
(1) x and y are consecutive numbers.
Case 1: Say x is even; thus, y is odd and (x - 1) is odd. Thus, y(x - 1) = Odd*Odd = Odd. The answer is no.
Case 2: Say x is odd; thus, y is even and (x - 1) is even. Thus, y(x - 1) = Even*Even = Even. The answer is yes.
No unique answer. Insufficient.
(2) y is odd.
Insufficient as we do not have any information about x.
(1) and (2) together
Only Case 1 discussed in Statement 1 is applicable; thus, (xy - y) even. Sufficient.
The correct answer:
C
Hope this helps!
-Jay
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