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Pastimes : My House
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To: Lazarus_Long who wrote (4514)1/23/2003 3:45:12 PM
From: Lazarus_Long  Read Replies (1) of 7689
 
Time to solve that thing.

Let the car and train start at time 0 and travel for t hours when they are 100 miles apart.

The train will have gone 50t miles. The car will have gone 60t miles.

Since one is going north and the other west, they are traveling at a right angle (90 degrees) to each other and the Pythagorean theorem applies. So

c = sqrt( a^2 + b^2)

100 = sqrt( (50t)^2 + (60t)^2 ) = sqrt ( (2500t^2 + 3600t^2) ))

100 = sqrt ( 6100t^2)

100 = 10t*sqrt(61)

t = 100/(10*sqrt(61))

t = 10/sqrt(61)

t = 1.28 hours = 1 hour 17 munutes approx.

Easy, right?
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