Any Lateral Thinkers Out There?

[Recco]

Heya.
Just picked up a book "Lateral Thinking Puzzles"
And i spotted one question that has caused me to say "WTF?"

"A Car is driven from A to B at a average speed of 60mph and is then driven back from B to A along the same route at an average speed of 40mph.
What is the average speed of the car for the whole journey?"

Now, most of use would say 50mph...well i would, but as i stumbled onto the anwers page and apparently the answer is 48mph...
I'm not one to question the validity of the answer, but could someone please explain to me how they came to the conclusion of 48mph.
Sorry to be a nuisance, but please put a young mind at rest.

[unreal]

Well if it's travelling at 40mph back, then it's going to take longer than the original way there. So say theres like in total 40% of the time taken was at 60mph, and 60% of the rest of total time was going at 40mph

Then you use that to work out the average.

[Dougal]

The reason is this:

say A-B takes 1hr, total distance 60m.

Travelling B-A at 40mph the journey takes 1hr 30mins.

so 120mile/2.5hr = 48mph

[Recco]

Thanks Unreal for the quick reply, I kinda understand your point of view, i always thought the 60mph would compensate the other route...guess this is a pretty useless thread.

Thanks again!

[unreal]

Ha no problem, it's not usual I do something intelligent so its a change

[5lab]

it depends whether you are determining average speed per distance or per time

or osmething

[Tumble]

err.. not really as speed is a ratio of distance over time..... so it's both

[Stoo]

classic

[menthel]

My brain hurts! Its all gone a bit Gumby up there.

[Theo]

Forgot to take into account the speed at which you turn the car around.

[Dav0s]

and if you meet godzilla on the way back who halts your car with his foot

or if you get stuck at lights

or if you get stopped by police


etc etc

[5lab]

depends what average. median would be 40..

[Howard]

unreal, your sig is tiny. You may wanna make it bigger so we can all see it

[kidzer]

exactly! FLAWS!

Its embarassing to a lot of people, its blatantly obvious once you know the answer, until then its horribly frustrating though

[Stewart]

Ha no problem, it's not usual I do something intelligent so its a change

Shrink that sig down, fool, or I'll get compton on your ass. And believe me, sukka, neither of us wants that.

[Recco]

Forgot to take into account the speed at which you turn the car around.

But would it really decrease the average speed by 2mph?
Maybe 0.5mph...man all confused again....