If y = 30p, and p is prime, what is the greatest common factor of y and 20p, in terms of p?  Pick: A) p B) 2p C) 5p D) 10p E) p^2
y = 30p = 2*3*5*p   20p = 2^2*5*p   The greatest common factor of 30p and 20p is the product of all the common prime factors, using the lower power of repeated factors. The greatest common factor is 2*5*p = 10p   The answer is 10p.
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If y = 30p, and p is prime, what is the greatest common factor of y and 20p, in terms of p?