Question

A truck gets 377/x mpg when driven at a constant speed of x mph (between 25 and 75 mph). If the price of fuel is $1 per gallon and the driver is paid $8 per hour, at what speed between 25 and 75 mph is it most economical to drive? (Give your answer correct to the nearest full mph)

Answer 1

cost=8*time+ x/(377/x)*$1/gallon*time

x is in miles/hr, t is in time hrs

d cost/dtime=0=8+ 377/x

solve for x, the most economical speed to drive.

x=377/8= ???

Answer 2

47