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Re: prime numbers........... [#permalink]
06 Apr 2009, 22:36

n = 5k. (n is a multiple of 5) n = p^2.q (Where p and q are prime numbers)

This means, either p or q is 5 because n is a multiple of 5 afterall. NOTE: It can be EITHER of them. Now we want multiple of 25 which is equal to 5^2. Thus: Q = 5^2 . z (We need to find the multiple Q where z is a constant)

Now look at the options: Can Q equal p^2? It could but we are not sure that p=5. Can Q equal q^2? It could but we are not sure that q=5. Can Q equal pq? No because we need 5 at least with an exponent of 2. Can Q equal p^2q^2? YES. At least one of them is 5^2!! Can Q equal p^3q? Again, what if q=5? In that case, we will be lacking one exponent of 5

Hence D it is Hope this helps.

gmatclubot

Re: prime numbers...........
[#permalink]
06 Apr 2009, 22:36

Harvard asks you to write a post interview reflection (PIR) within 24 hours of your interview. Many have said that there is little you can do in this...