Question

5) A solid is composed of a cylinder with hemispherical ends. If the whole length of the solid is 100 cm
and the diameter of the hemispherical ends is 28 cm, find the cost of polishing the surface of the solid at
the rate of 5 paise per sq. cm.​

Answer 1

Answer:

The cost of polishing the surface of the solid is Rs.1126.4.

Explanation:

Given that, r, radius of the cylinder= radius of the hemispherical ends= 28 cm

h, height of the cylinder= (100-28)= 72 cm.

total surface area

= curved surface are of the cylinder + surface areas of hemispherical ends

=(2πrh+2×2πr²)cm²=(2πrh+4πr²)cm²=2πr(h+2r)cm²

= 2×22/7×28×72+ 4×22/7×28×28= 22528 cm²

Rate of polishing 5 paise per sq.cm

Cost of polishing =Rs. 22528× 5÷100 =Rs.1126.4 Rs

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