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Number Properties Question

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Number Properties Question

by KICKGMATASS123 » Mon May 18, 2009 5:00 pm
Really have no idea about this one!

If n is a multiple of 5 and n = p^2 *q where p & q are prime numbers, which of the following must be a multiple of 25?

a. p^2
b. q^2
c. pq
d. p^2q^2
e. p^3q

OA is D
Last edited by KICKGMATASS123 on Mon May 18, 2009 6:21 pm, edited 1 time in total.
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by ManSab » Mon May 18, 2009 5:06 pm
B:

let us say
p = 2
q = 5
both prime

n= 2^2 * 5
n = 20 which is multiple of 5.

so the multiple of 25 would be
q^2 , in above case 5^2 = 25

Correct me if I am wrong

Thanks
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by francopiccolo » Mon May 18, 2009 5:09 pm
n is a multiple of 5, thus p or q are equal to 5.

For x to be a multiple of 5, x must contain twice the factor 5.

In p^2q^2 we have twice p and twice q therefore we have twice the factor 5, we don't know if thanks to p or thanks to q, but that is the right answer.
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