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the joker

18th January 2010, 19:02
As we seem to have veered to include numerical problems on the site,here is one for all you motorists(and others).

There is a hill one mile up and one mile down the other side.

A car drives up the hill at a speed of 30mph. At what speed does it have to travel down hill to average 60mph over the whole journey?
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wordsmith

18th January 2010, 19:06
90 mph? the fact it is a hill is irrelevant, isn't it?
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helena

18th January 2010, 19:12
i'm with wordsmith with the answer
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the joker

18th January 2010, 19:15
Sorry Wordsmith and Helena. Not the correct answer.
TJ
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harrhy

18th January 2010, 19:25
He has to travel 2 miles in two minutes to average 60mph over the whole distance. He has already taken 2 minutes to get to the top at 30mph therefore it is impossible for him to get there in time without travelling at infinite speed.
Have I got ths completely wrong?
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trevor

18th January 2010, 19:25
I think it is not possible.
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trevor

18th January 2010, 19:26
same reasoning as Harrhy
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terry

18th January 2010, 19:29
Harrhy and trevor are right. Harrhy's explanation or should I say proof is spot on.
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helena

18th January 2010, 19:31
doh, a bit technical for me
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harrhy

18th January 2010, 19:32
That's a relief! Average speeds are always more complicated than they look:-)
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