Question

A solid is composed of a cylinder with hemispherical end if the whole length of solid is 114cm and the radius of each hemispherical end is 7cm then find the cost of polishing surface at the rate of rupees 2 per dm square​

Answer 1

Hemispherical part: r=7cm

Cylindrical part: r=7cm,h=104−(7+7)=90cm

Total surface area of the solid= CSA of cylindricall part+2×CSA of hemispherical part

=2πrh+2×2πr

2

=2πr(h+2r)

=2×

7

22

×7[90+2(7)]cm

2

=44×104cm

2

=4576cm

2

∴ TSA of the solid=4.576cm

2

Cost of polishing at the rate of Rs.4 per 100cm

2

=4576×

100

Rs.4

=Rs.183.04

∴ Cost of polishing the solid=Rs.183.04.

solution

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