Question

A solid right circular cylinder of radius 8 cm and height 3cm is melted to make a cone of height 3 times that of cylinder, find the curved surface area of the cone.

Answer 1

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Answer 2

Answer:

Volume of Cylinder = πR^2h

Volume of Cone = 1/3 πr^2h

Height of Cylinder = 3 cm

So, Height of Cone = 3 x 3 = 9 cm

π x 8 x 8 x 3 = 1/3 π x r^2 x 9

r^2 = 8 x 8 x 3 x 3/9 = 64 x 3 x 1/3 =  64

Therefore, r = √64 = 8 cm.

l = √r^2+h^2 = √64 + 81 = √145 = 12.04 cm

Hence, CSA = πrl

= 22/7 x 8 x 12.04

= 302.76 cm2