GMAT Prep 2?? (multiple)

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Source: — Data Sufficiency |

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by codesnooker » Wed May 14, 2008 6:31 pm
Answer is (C)

Condition 1: n is multiple of 20 (not sufficient, lets say n = 20, which is not multiple of 15)

Condition 2: n + 6 is multiple of 3 (not sufficient, lets say n = 3, which is not multiple of 15)

Let try both conditions together:

From condition n could be 20, 40, 60, 80, 100, 120......

On applying condition 2 on the above dataset, our dataset would be reduced
to 60, 120, 180......

which is divisible by 15.

Hence both conditions together are sufficient. (C)