Question

Q.The radii of the ends of a frustum of a cone 4m high are 7m and 4m.find its volume and curved surface area?????

Answer 1

CSA of a frustum =πl(R+r)

Slant height (l)^2=h^2+(R-r)^2

Slant height (l)^2 = 4^2+(7-4)^2

                   l=5

R=7

R=4

H=4

L=5

CSA of frustum = 22/7*5(7+4)

                              22/7*55=172.857

volume =πh/3(R^2+r^2+Rr)

       22/7/3(7^2+4^2+7*4)

    389.7142 m^3