It has taken me 4+ min to solve. I'm sure there is a method to solve those even\odd DS's.
can't imagine sitting on those Q's more than 2.5 min each in the real GMAT. would any of you people like to share a method for those kind of Q's
If a and b are integers, is b even?
(1) 3a + 4b is even
(2) 3a + 5b is even
I'm less interested in the final answer, more in the way so please explain.
asalways, OA will follow.
1.4b is even, no matter what b is!, and 3a+4b is even, so a must be even. No fixed about b, -> not sufficient
2. 3a + 5b even
2.1 even +even =even
2.2 odd +odd = even
so b can be even or odd --> not sufficient
1 and 2 combined is sufficient
from 1, we know a is even, so 3a must be even, and 3a +5b is even, therefore, b must be even --> sufficient
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