SOLUTION: Two trains going in opposite directions leave at the same time. Train B travels 25 mph faster than train A. In 6 hours the trains are 690 miles apart. Find the speed of each.

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Two trains going in opposite directions leave at the same time. Train B travels 25 mph faster than train A. In 6 hours the trains are 690 miles apart. Find the speed of each.      Log On


   

Question 1045838: Two trains going in opposite directions leave at the same time. Train B travels 25 mph faster than train A. In 6 hours the trains are 690 miles apart. Find the speed of each.
Answer by ikleyn(52756) About Me  (Show Source):
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Two trains going in opposite directions leave at the same time. Train B travels 25 mph faster than train A. In 6 hours the trains are 690 miles apart. Find the speed of each.
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Let x be the speed of the train A and y be the speed of the train B.
Then

(1) b - a = 25,  and
(2) b + a = 690%2F6 = 115.

One more time:

(1) b - a = 25,  and
(2) b + a = 115.

Add the equations (1) and (2) (both sides). You will get

2b = 25 + 115  --->  2b = 140  --->  b = 140%2F2  --->  b = 70.

Then a = b - 25 = 70 - 25 = 45.

Answer.  The train A speed is 45 mph.  The train B speed is 70 mph.