Question

The radii of two cylinders are in the ratio 3:4 and their heights are in the ratio5:3. Find the ratio of their curved surface areas.

Answer 1

Let 2x and 3x be the radii of the two cylinders
and their height be 5y and 3y respectively

now
C.S.A of first cylinder (a) = 2 × 22/7 × 2x × 5y
C.S.A of second cylinder (b) = 2 × 22/7 × 3x × 3y
ratio of them = a/b
= (2 × 22/7 × 2x × 5y)/(2 × 22/7 × 3x × 3y)
= 10xy / 9xy
= 10/9
therefore their C.S.A are in the ratio 10:9