difficult sum

Asked by  | 21st Oct, 2008, 06:02: PM

Expert Answer:

I think , you mean

a cylinder and a cone have equal radii of their bases and equal heights. if their curved surface areas are in the ratio 8:5 then show that the ratio of the  radius of each  to the  height of each as 3:4

 2 pi r h / pi r l = 8/ 5

 i.e 2h /l = 8/5

i.e h / sq root ( h 2 + r 2) = 4/5

Squaring and cross multiplying , we get

25h2 = 16 ( h 2 + r 2)

(25 - 16 ) h2 = 16 r 2

9h2 = 16 r 2

 r 2 / h 2 = 3 9/16

r/ h = 3/4

Answered by  | 21st Oct, 2008, 06:41: PM

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