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Re: Is the integer z divisible by 6? [#permalink]
23 Feb 2012, 14:25
Is the integer z divisible by 6?
Realistic GMAT question would mention that z is a positive integer.
(1) The greatest common factor of z and 12 is 3 --> if z were divisible by 6 (for example 6, 12, 18, ...) then the GCF of z and 12 (which is also divisible by 6) would have been more than 3 (6 or 12) and since the GCF is 3 then z is not divisible by 6. Sufficient.
(2) The greatest common factor of z and 15 is 3 --> if z=3 then the answer is NO but if z=6 then the answer is YES. Two different answers, not sufficient.