Help with a question (1 Viewer)

[abdog]

The cost of running a car at an average speed of V km/h is given by C=150+(v2/80) cents per hour. Find the average speed, to the nearest km/h, at which cost of a 500km trip is a minimum. Where do I even start?

 

[braintic]

(Assuming v2 means V^2)

Time for a 500 km trip at V km/h is 500/V hrs.

Cost = (cost/hr) times (number of hrs)
= [150 + (v^2)/80] times 500/V
= 500 [150V^(-1) + V/80 ]

This is the equation you have to differentiate.

 

[Breeby]

Oh wow. I did 4u maths and I've seriously forgotten EVERYTHING :/

 

[abdog]

Can you explain everything in a simpler way? I seriously don't know how you got that equation....