Question:
The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find:
(a) Inner curved surface area
(b) The cost of plastering this curved surface at the rate of Rs 40 per $m^{2}$.
Solution:
The inner diameter of the well = 3.5 m
Inner radius = 3.52 = 1.75 m
Height of the well = 10 m
(a) Inner curved surface area
= 2πrh
= 2 * 3.14 * 1.75 * 10
$=110 m^{2}$
(b) Cost of painting $1 \mathrm{~m}^{2}$ area of the well
= Rs 40
Cost of painting $110 \mathrm{~m}^{2}$ area of the well
= Rs (50*110) = Rs 4400