Question

A petrol tank is in the form of a frustum of a cone of height 20 m with diameters of its

lower and upper ends as 20 m and 50 m respectively. Find the cost of petrol which can

fill the tank completely at the rate of Rs. 70 per litre. Also find the surface area of the

tank.

​

Answer 1

$Capacity \: of \: tank \: \\ = 1/3π x 20 x (102 +252 +10 x 25)m3 π x 20 x 325 m3 = π x 20 x 325 l Cost of petrol = π x 20 x 325 x 70 = Rs.1430000 Slant height = √(202 +(25 -10))2 = 25 Surface area of tank = π x 25 (10 +25 )m2 = 2750m2$