Word problem: cost of running a train at speed v....

[Guest]

THe cost of running a train at a constant speed of v km/h is

C = 50 + v^2 /1000 $ per hour

a) Find the time taken for an 800km journey in terms of v
b) Hence find an expression for the cost of an 800km journey
c) Find the most economical speed for this journey


t/u in advance...

 

[tkhunny]

You need: Distance = Rate * Time

You have:

v: A constant speed.
Distance: 800 km

Solve for "Time".