SOLUTION: Two trains are 500 miles apart. They start towards eachother at the same time,one's speed is 20 miles per hour faster than the other.Thet meet in 4 hours.How fast is each train goi

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Question 443749: Two trains are 500 miles apart. They start towards eachother at the same time,one's speed is 20 miles per hour faster than the other.Thet meet in 4 hours.How fast is each train going?
Found 2 solutions by josmiceli, htmentor:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Think of 1 train as standing still and the other
heading towards it at the sum of their speeds
Let the speed of the slower train = s
+d+=+r%2At+
+500+=+%28s+%2B+s+%2B+20%29%2A4+
+500+=+%282s+%2B+20%29%2A4+
+500+=+8s+%2B+80+
+8s+=+420+
+s+=+52.5+
+s+%2B+20+=+72.5+
The slower train is going 52.5 mi/hr
The faster train is going 72.5 mi/hr
check amswers:
slower train:
+d+=+52.5%2A4+
+d+=+210+
faster train:
+d+=+72.5%2A4+
+d+=+290+
+210+%2B+290+=+500+
+500+=+500+
OK

Answer by htmentor(1343) About Me  (Show Source):
You can put this solution on YOUR website!
Let s = the speed of train A
Then s + 20 = the speed of train B
The distance traveled by train A is:
d = s*t -> d = 4s
The distance traveled by train B will be 500 - d.
Therefore, 500 - d = (s + 20)t = (s + 20)4
We have two equations in two unknowns. Since we need to find s, we want to eliminate d:
d = 4s [1]
500 - d = 4s + 80 [2]
Use the value expression for d in [1] and substitute into [2]:
500 - 4s = 4s + 80
8s = 420 -> s = 52.5
So, the speed of train A = 52.5 mph
The speed of train B = 52.5 + 20 = 72.5 mph