If the radius of a cylinder is doubled and height 5 times, what is the new volume of the cylinder divided by the old one?  Answers:
A) 8.
B) 2.
C) 6.
D) 20.
E) 10.
let v and v' be the original and the changed volume   now   v=pir^2h   v'=pi(2r)^2(5h)   v'=20v   20.) 20
<result>D</result>
If the radius of a cylinder is doubled and height 5 times, what is the new volume of the cylinder divided by the old one?