Hi,
The answer is C) but I am not too sure why A) is a necessary information - please explain... thanks!
If x and y are positive integers and x is a multiple of y, is y = 2?
(1) y ≠ 1
(2) x + 2 is a multiple of y.
ds test4 #23
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- jayhawk2001
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We are given x = my
1 - insufficient. Just knowing y != 1 does not help
2 - insufficient. We have x+2 = ny. Subtracting the 2 equations,
we get
x+2 - x = ny - my
or (n-m)y = 2
Since we are dealing with +ve integers here, we have 2 possibilities
n-m = 2, y = 1
n-m = 1, y = 2
Taking 1 and 2 together, we know that y!=1, so it boils down to
n-m = 1, y = 2
Hence C
1 - insufficient. Just knowing y != 1 does not help
2 - insufficient. We have x+2 = ny. Subtracting the 2 equations,
we get
x+2 - x = ny - my
or (n-m)y = 2
Since we are dealing with +ve integers here, we have 2 possibilities
n-m = 2, y = 1
n-m = 1, y = 2
Taking 1 and 2 together, we know that y!=1, so it boils down to
n-m = 1, y = 2
Hence C