Question

From a solid cylinder of height 20 cm and diameter 12 cm, a conical cavity of height 8 cm and radius 6 cm is hollowed out. Find the total surface area of the remaining solid. (Use $\pi = \frac{22}{7}$)

Answer 1

d of sphere is 21cm

r of sphere is 10.5cm

r of cone is 3.5cm

h of cone is 3cm

no. of cones = v of sphere / v of cone

no.of cones = 4/3 pi r cube/1/3 pi r square h

=> 4/3 *22/7 *10.5 *10.5 *10.5 = 1/3 *22/7 *3.5 *3.5 *3

=> 4851 cm cube = 38.5 cm cube

no of cones = 4851 cm cube / 38.5 cm cube

no of cones =126 ans..