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April 19, 2014

April 19, 2014

Posted by **Raz** on Sunday, September 22, 2013 at 5:07pm.

Note:

The racetrack is 'circular' in the sense that the start and end points are the same, and the cars are running laps around the racetrack at a constant speed.

- Math -
**Steve**, Sunday, September 22, 2013 at 6:41pmIf the track has circumference c miles, then and the car's speeds are x and y mi/s, then since time = distance/speed,

In the same direction, the slow car has a "lead" of 1 mile which the faster car has to make up.

1/(y-x) = 120

1/(x+y) = 30

120(y-x) = 30(x+y)

120y-120x = 30x+30y

90y = 150x

y = 5/3 x

1/(x + 5/3 x) = 30

8/3 x * 30 = 1

80x = 1

x = 1/80 mi/sec = 45 mph

y = 75 mph

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