SOLUTION: 1. Two trains leave a city, traveling in opposite directions. One train is 20 mph faster than the second. After 5 hours the trains are 800 miles apart. What is the speed of each tr

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Question 649316: 1. Two trains leave a city, traveling in opposite directions. One train is 20 mph faster than the second. After 5 hours the trains are 800 miles apart. What is the speed of each train? can u tell me the formula to solve this.. and how to do it without distance.. been trying for hours and I have a final tommorow!!
Answer by MathTherapy(10557) About Me  (Show Source):
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1. Two trains leave a city, traveling in opposite directions. One train is 20 mph faster than the second. After 5 hours the trains are 800 miles apart. What is the speed of each train? can u tell me the formula to solve this.. and how to do it without distance.. been trying for hours and I have a final tommorow!!

Let the speed of the slower train be S
Then the speed of the faster train = S + 20

Distance traveled by slower train, plus distance traveled by faster train = distance apart, OR

5S + 5(S + 20) = 800

5S + 5S + 100 = 800

10S = 800 - 100

10S = 700

S, or speed of slower train = 700%2F10, or highlight_green%2870%29 mph

Speed of faster train = 70 + 20, or highlight_green%2890%29 mph

OR

Time * sum of speeds = distance apart

5(S + S + 20) = 800

2S+%2B+20+=+800%2F5

2S + 20 = 160

2S = 140 ----- S = 140%2F2, or 70 mph (slower)
70 + 20, or 90 mph (faster)

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