If p and r are integers, and p^2 = 20r, then r must be divisible by which of the following?  Pick.
A) 2 B) 4 C) 5 D) 7 E) 14
Ans: D   Solution: for p to be an int 20 r must be whole square of a number.   20r= 5*2*2*r   to make it whole square we need 5   so r can must be divisible by 5y where y is itself a whole square.   so 5 is the ans
<result>C</result>
If p and r are integers, and p^2 = 20r, then r must be divisible by which of the following?