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#1 brhan

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Posted 20 February 2008 - 05:41 PM

A car travels downhill at 72 km per hr, on the level at 63 km per hr, and uphill at 56 km per hr. The car takes 4 hours to travel from town A to town B. The return trip takes 4 hours and 40 minutes. What is the distance between the two towns.
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#2 Enlightened

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Posted 20 February 2008 - 06:38 PM

Spoiler for solution

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#3 PolishNorbi

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Posted 20 February 2008 - 06:53 PM

Spoiler for Spoiler

Edited by PolishNorbi, 20 February 2008 - 06:53 PM.

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#4 bonanova

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Posted 20 February 2008 - 09:31 PM

A car travels downhill at 72 km per hr, on the level at 63 km per hr, and uphill at 56 km per hr. The car takes 4 hours to travel from town A to town B. The return trip takes 4 hours and 40 minutes. What is the distance between the two towns.

Can we assume that the road from A to B has a constant grade?
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#5 Aatif

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Posted 21 February 2008 - 02:37 AM

Can we assume that the road from A to B has a constant grade?

Bonanova, I think you don't need to assume that A to B have constant grade, but you do need to assume (or maybe its given) that he drives at constant speed of 72kmph downhill, regardless of the gradient and 56kmph uphill regardless of the gradient .
Spoiler for A graded problem

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#6 brhan

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Posted 21 February 2008 - 12:26 PM

Can we assume that the road from A to B has a constant grade?


You may assume that the car travels at constant speed during the three events. That is, at constant speed of 72 km per hr on the downhill, at 63 km per hr on the level, and at 56 km per hr on the uphill.
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