If the inner curved surface of the well in part (i) above is to be plastered at the rate of ₹ 300 per m², find the cost of plastering (around to the nearest hundred rupees).

By formula,

Curved surface area of cylinder = 2πrh

$\text{Curved surface area of cylinder }= 2 \times \dfrac{22}{7} \times 1 \times 20 \\[1em] = \dfrac{880}{7} m^2$

Rate of plastering = ₹ 300/m².

Cost of plastering = Curved surface area of cylinder x Rate

= $\dfrac{880}{7} \times 300 = \dfrac{264000}{7} = 37,714.28 \approx$ ₹ 37,700

Hence, the cost of plastering the inner curved surface area of the well = ₹ 37,700.