GMAT Problem Solving (PS) | Re: How many factors of 240 are also multiples of 3 ?

Factorize 240: 240=2^4*3*5. It has (4 + 1)(1 + 1)(1 + 1) = 20 factors.

Get rid of 3, we get 80 =2^4*5. It has (4 + 1)(1 + 1) = 10 factors.

Now, all these factors of 80 are factors 240 but are NOT multiples of 3. So, the number of factors of 240 which are also multiples of 3 is 20 - 10 = 10.

Answer: D.

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