Question

If g(v) is the fuel efficiency of a car travelling at v kilometres per hour ( that is g(v) is the number of litres used per 100 kilometres when travelling at v kph), what is the practical significance of the statement: g'(90) = 0.21?

Thanks!

Answer 1

In general for a function f, what does f'(a) mean? What does it mean if it is positive?

Answer 2

I'll tell you: Among other things, f'(a) > 0 means that f(a) is increasing at x = a as x increases beyond a

So if at a = 90 kmh, g'(90) = 0.21 > 0, it means you are using MORE or LESS fuel as you go faster than a = 90 kmh.

Which of MORE or LESS is correct?

Answer 3

Thanks, for the reply,
and sorry for the late reply, though it would be more fuel because its increasing due to its sign?

Answer 4

Yes exactly. So in other words, the car is getting less fuel efficient as you drive faster than 90 kmh.

Answer 5

Ohh i get it now, thanks a lot for your help, i appreciate it