(15.) A toy is in the shape of a cone mounted on a hemisphere of same base radius. If the volume of the toy is 231 cm and its diameter is 7 cm, find
the height of the toy.

Given:

Volume of toy=231 cm³

Diameter of a hemisphere= 7 cm

cone and hemisphere have equal radius.

radius of hemisphere = radius of cone = 3.5 cm

Height of hemisphere= radius of hemisphere= 3.5 cm

Let H be the height of toy

H= height of cone+ height of hemisphere

H = h + r , ( h = height of cone)

H = h + 3.5

volume of toy = volume of cone + volume of hemisphere

Volume of toy= 1/3πr²h + 2/3πr³

Volume of toy=πr²/3(h+2r)

231 = (22/7)×(3.5)² ×(1/3)(h+2×3.5)

231×3 =( 22×3.5×3.5)/7 (h+7)

h+7 = (231×3×7)/(3.5×3.5×22)

h+7 = (3×3)/(.5×.5×2)

h+7= 900 /50= 90/5= 18

h+7= 18

h=18-7

h= 11 cm

Height of toy = h+r

Height of toy = 11+3.5= 14.5

Height of toy =14.5 cm

Hence, the height of the toy = 13.5 cm

The answer is