If the diameter of circle R is 80% of the diameter of circle S, the area of circle R is what percent of the area of circle S? Select
A) 74% B) 64% C) 84% D) 94% E) 34%
Let diameter of circle R , dr = 80   and diameter of circle S , ds = 100   Radius of circle R , Rr = 40   Radius of circle S , Rs = 50   Area of circle R/ Area of circle S = (pi * Rr ^2 ) /( pi * Rs^2 )   = (40/50)^2 = (8/10)^2   =64%   Answer :64%
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If the diameter of circle R is 80% of the diameter of circle S, the area of circle R is what percent of the area of circle S?