(1) Let x = 3 and y = 2, then x(y + 1) = 3*(2 + 1) = 9, which is odd.
Let x = 2 and y = 11, then x(y + 1) = 3*(5 + 1) = 12, which is even.
No unique answer.
So, (1) is NOT SUFFICIENT.
(2) Let x = 2 and y = 11, then x(y + 1) = 2*(11 + 1) = 24, which is even.
Let x = 3 and y = 10, then x(y + 1) = 3*(10 + 1) = 33, which is odd.
No unique answer.
So, (2) is NOT SUFFICIENT.
Combining (1) and (2), we get
x and y are prime numbers such that y > 7.
y will always be odd as y > 7, so (y + 1) will always be even as ODD + ODD = EVEN
x can be even or odd. So, EVEN * EVEN = EVEN
ODD * EVEN = EVEN
In both the cases, x(y + 1) is even.
The correct answer is [spoiler](C)[/spoiler].
DS: algebra
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Source: Beat The GMAT — Data Sufficiency |
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Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
