# Mensuration-52

### From Homeworkwiki

**A solid is composed of a cylinder with hemispherical ends. If the whole length of the solid is 108 cm,and the diameter**

**of the hemispherical ends is 36 cm, find the cost of polishing the surface at the rate of 7 cents per square cm.**

**Solution:** Radius of the cylinder = Radius of the two hemispheres = 36/2 cm = 18 cm

Length of the cylinder = (108 - 18 - 18) cm = 72 cm

Surface area of the cylinder = 2 Π r h

Total surface area of the two equal hemispheres = 4 Π r^{2}

Surface area of the whole solid

= 2 Π r h + 4 Π r^{2}

= 2 Π r (h + 2r)

= 2 x 3.1416 x 18 (72 + 2 x 18)

= 12214.54 cm^{2} (approx)

Therefore, cost of polishing = $ (7/100 x 12214.54) = **$855.02**