Question

A toy is in the form of a cylinder with hemispherical ends. If the whole length of the toy is 90 cm and its diameter is 42 cm, find the cost of painting the toy at the rate of 70 paise per sq cm.

Answer 1

Diameter = 42 cm
So, radius= 21 cm
Height of cylinder part = 90 - (21+21) = 48 cm

Surface area of toy = CSA of cylinder + 2 $\times$ CSA of each hemisphere

$=2\pi rh+2\times 2\pi r^2$

$=2\pi r(h+2r)$

$=2\times \frac{22}{7}\times 21\times (48+2\times 21)$

$=132\times 90$

$=11880c{m}^2$

So, total cost = $11880\times 0.7=Rs.8316$