Question

a tank is 20m in length 15m breadth and 4m in depth find the cost of cementing its floorand the four walls at the rate of 50 per s.m

Answer 1

length of cuboid = 20 m
breadth of cuboid= 15 m 
depth of cuboid = 4 m
Area of 5 faces of cuboid= 2h(l+b) + lb
= 2 x 4 (20 +15) + 20 x 15
= 8 x 35 + 300
= 280 + 300
= 580 sq. m

Total cost of cementing walls at the rate of rs. 50 per sq. m= 580 x 50 = rs. 29000

∴The total cost of cementing will be rs. 29000