Question

a tank is 30 m long, 9 m long wide and 4 m deep. what is the cost of plastering it's walls and bottom at 25 paise per square m?

Answer 1

Rs. 270 will be the cost.

Answer 2

area of walls and bottom = 2(lb+bh+hl) - lb   [subtracted top area from total surface area]
= 2*(30*9 + 9*4 + 4*30) - 30*9
= 2*(270 + 36 + 120) - 270
= 2*(426) - 270
= 852 - 270
= 582$m^{2}$
cost = Rs.(1/4 * 582)
= Rs.145.5