Bunuel wrote:
If a and b are positive integers, is a/b an integer?
(1) a > b
(2) a and b share only one factor.
Target question: Is a/b an integer? Given: a and b are positive integers Statement 1: a > b This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of a and b that satisfy statement 1. Here are two:
Case a: a = 2 and b = 1, in which case
a/b = 2/1 = 2, and 2 IS an integerCase b: a = 3 and b = 2, in which case
a/b = 3/2, and 3/2 is NOT an integerSince we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: http://www.gmatprepnow.com/articles/dat ... lug-values Statement 2: a and b share only one factor There are several values of a and b that satisfy statement 2. Here are two:
Case a: a = 2 and b = 1, in which case
a/b = 2/1 = 2, and 2 IS an integerCase b: a = 3 and b = 2, in which case
a/b = 3/2, and 3/2 is NOT an integerSince we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined There are several values of a and b that satisfy BOTH statements. Here are two:
Case a: a = 2 and b = 1, in which case
a/b = 2/1 = 2, and 2 IS an integerCase b: a = 3 and b = 2, in which case
a/b = 3/2, and 3/2 is NOT an integerSince we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
Cheers,
Brent
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