Question

The fuel charges for running a train are proportional to the square of the speed generated in miles per hour and costs Rs. 48 per hour at 16 miles per hour. The most economical speed if the fixed charges i.e. salaries etc. amount to Rs. 300 per hour is

(a) 10 (b) 20 (c) 30 (d) 40

Answer 1

Correct option (d) 40

Explanation:

Let the speed of the train be v and distance to be covered be so that total time taken is /v hours. Cost of fuel per hour = kv2 (k is constant)

Also 48 = k. 162 by given condition