Question

38) A cone and a hemisphere are joined on either sides of a cylinder. These
solids have radius 7cm each. If the total height of the solid is 61cm and
the height of the cylinder is 30cm, find the cost of painting the outer
surface of the solid at the rate of Rs. 10 per 100cm.
ans this question pls and give reason.​

Answer 1

★. Correct Question . ★

A cone and a hemisphere are joined on either sides of a cylinder. These

solids have radius 7cm each. If the total height of the solid is 61cm and

the height of the cylinder is 30cm, find the cost of painting the outer

surface of the solid at the rate of Rs. 10 per 100cm.

$\rule{300}2$

★ Solution

$\rule{300}2$

Height of solid = height of cylinder+height of cone + height of hemisphere.

61= 30+height of cone + 7

height of cone = 61 -37

height of cone = 24

$\rule{300}2$

t.s.a of solid = C.S.A of cone + C.S.A of cylinder + C.S.A of hemisphere.

t.s.a of solid = πrl+2πrh+2πr

t.s.a of solid $\longrightarrow l^{2}=\sqrt{24^2+7^2}$

$\longrightarrow \sqrt{576+59} \\ \longrightarrow \sqrt{625} \\ \longrightarrow l=25$

t.s.a of solid = C.S.A of cone + C.S.A of cylinder + C.S.A of hemisphere.

T.S.A= πrl+2πrh+2πr

$\longrightarrow \frac{22}{7}×7×25+2×\frac{22}{7}×7×30+2×\frac{22}{7}×7 \\ \longrightarrow 22×25+2×22+30+2×22 \\ \longrightarrow 1914cm^{2}$

$\rule{300}2$

cost = $\longrightarrow \frac{1914×10}{100} \\ \longrightarrow = 191.4ruppes$