Thread: Word Problem

Hey all, this question has been bugging me for two days, it feels like i can see the solution but i can't quite put my finger on it.

1.) A car travels half the distance of a journey at an average speed of 80km/h and half at an average speed of x km/h.

Define a function, S, which gives the average speed for the total journey as a function of x.

Thanks in advance.

Originally Posted by andrew2322

Hey all, this question has been bugging me for two days, it feels like i can see the solution but i can't quite put my finger on it.

1.) A car travels half the distance of a journey at an average speed of 80km/h and half at an average speed of x km/h.

Define a function, S, which gives the average speed for the total journey as a function of x.

Thanks in advance.

Maybe I do not understand you correctly, but if half the journey was at 80 km/h and the other half at km/h, then wouldn't it simply be:



Which if you want to write as a function of can be written as:

hello, that was my initial intention however, it was wrong, wrong and wrong again.

I've tried so many different ways of working it, its so frustrating!!

Let the total distance travelled is D

So time taken while travelling with 80kmph =
and time taken by travelling with x kmph =
Function is given by



Go ahead cancel D and simplify

Originally Posted by janvdl

Maybe I do not understand you correctly, but if half the journey was at 80 km/h and the other half at
km/h, then wouldn't it simply be:

not true in this case
It won't be correct
Never try to average the averages

THATS EXACTLY WHAT I DID! well... several times atleast, then i tried many, MANY different other methods and they were all wrong too.

Originally Posted by andrew2322

THATS EXACTLY WHAT I DID! well... several times atleast, then i tried many, MANY different other methods and they were all wrong too.

what's the answer, because either your question is wrong or the answer