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From A to B (Posted on 2002-05-15) Difficulty: 5 of 5
A car drives downhill with the speed of 90 m/h. On a level road, the same car goes 72 m/h, and uphill it goes "only" 60 m/h.

It takes this car 5 hours to go from town A to town B. The return trip only takes 4 hours.

Find the distance between the two towns.

See The Solution Submitted by levik    
Rating: 3.8667 (15 votes)

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Simpler Algebra | Comment 10 of 14 |
x/60 + y/72 + z/90 = 5 and
x/90 + y/72 + z/60 = 4
multiply each equation by 360:
6x + 5y + 4z = 1800 and
4x + 5y + 6z = 1440
Add these two equations:
10x + 10y + 10z = 3240
Divide by 10:
x + y + z = 324
  Posted by Charlie on 2003-02-10 02:50:33
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