Data Sufficiency

If a, b are positive integers (b≠1), is a/b<1/10 ?
1) a/(b-1)<1/15
2) (a-1)/b<1/15

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Statement 1 -

a/b-1 < 1/15 ---> 15a + 1 < b since and b are positive --- > sufficient to say that 10a < b - SUFFICIENT

Statement 2 -

a-1/b < 1/15 ---> 15a - 15 < b. Put a = 2 and a= 5 and you will see that you get 2 answers for the original expression -- NOT SUFFICIENT

Since there are 2 variables in the original condition, there is a high chance that C is the correct answer. Applying the common mistake type 4(A), the correct answer is A.

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.