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# The inner diameter of a circular well is 3.5 m. It is 10 m deep. Findi) its inner curved surface areaii) the cost of plastering this curved surface at the rate of Rs. 40 per $${m}^2$$.

Given :
Inner radius (r) of circular well = $$\frac{3.5}{2}$$ m = 1.75 m
Depth (h) of circular well = 10 m

i) We know that,

Inner curved surface area
= $$2{\pi}rh$$
= $$2 × \frac{22}{7} × 1.75 × 10$$ $${m}^2$$
= (44 × 0.25 × 10) $${m}^2$$
= 110 $${m}^2$$

Therefore, the inner curved surface area of the circular well is 110 $${m}^2$$

ii) We have, Cost of plastering 1 $${m}^2$$ area = Rs. 40
Cost of plastering 100 $${m}^2$$ area = Rs. (110 x 40) = Rs. 4400

Therefore, the cost of plastering the CSA of this well is Rs. 4400.