(Q7).A storage tank consists of a circular cylinder with a hemisphere stuck on either end. If the external diameter of the cylinder be 1.4 m. and its length be 8 m. Find the cost of painting it on the outside at rate of Rs. 20 per m2.

Answer:

Total surface area of the tank = 2 × C.S.A. of hemisphere + C.S.A. of cylinder.

8m1.4m

Hemisphere:

Radius (r) =
d
2
 =
= m

C.S.A. of hemisphere = 2πr2.

= ×
× ×

= m2.

2 × C.S.A. = × m2 = m2

Cylinder:

Radius (r) =
d
2
 =
= m

Height (h) = 8 m

C.S.A. of the cylinder = 2πrh

= ×
× ×

= m2

∴ Total surface area of the storage tank = + = m2

Cost of painting its surface area @ Rs. 20 per sq.m, is

= × = Rs. .