Question

A cylindrical well is 21m deep. Its outer and inner diameters are 21m and 14m respectively. Find the cost of renovating the inner curved surface and outer curved surface at the rate of ₹25 per square metre.

Answer 1

CSA of inner side + CSA of outer side
2πrh+ 2πRh [ r = 14/2 = 7 m and R = 21/2 10.5 m] h = depth = 21 m
2πh(r+R)
2×22/7×21(7+10.5)
2309.07m^2
cost of renovating 1m^2 area = Rs.25
cost of renovating 528m^2 area = Rs.25×2309.07
Rs.57726.77