A well has to be dug out 20 m deep and its radius is 3.5 m. Find the cost of plastering the inner curved surface at ₹ 5 per square meter.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → ₹ 2,200
The inner wall of the well is the curved surface of a cylinder, whose area is \(2\pi rh\); the cost is that area times the rate per square metre.
Curved surface \(=2\times\frac{22}{7}\times3.5\times20=440\,\mathrm{m^2}\)
Cost \(=440\times5=\) ₹ 2,200