Circles X and Y are concentric. If the radius of circle X is six times that of circle Y, what is the probability that a point selected inside circle X at random will be outside circle Y? Choices
A) 13 B) Pi/3 C) Pi/2 D) 35/36 E) 8/9
Small circle radius = a, so area = PI a ^ 2   Large circle radius = 6a, so area = 9. PI a ^ 2   Area of shaded region = 36PI a^2 - PI a^2 = 35 PI a^2   So, probability = ( 35 PI a^2 ) / (36 PI a^2 )   = 35/36 = Answer = 35/36
<result>D</result>
Circles X and Y are concentric. If the radius of circle X is six times that of circle Y, what is the probability that a point selected inside circle X at random will be outside circle Y?