SOLUTION: An express and local train leave GraysLake at 3 P.M. and head for Chicago 50 miles away. The express travels twice as fast as the local and arrives 1 hour ahead of the local. Find

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Question 25708: An express and local train leave GraysLake at 3 P.M. and head for Chicago 50 miles away. The express travels twice as fast as the local and arrives 1 hour ahead of the local. Find the speed of each train.
Answer by Paul(988) About Me  (Show Source):
You can put this solution on YOUR website!
Let the speed of one train be x
Let the speed of the other be 2x
Since 50 miles is the distance with unknown speed = 50/x for slower train and 50/2x for the faster one.
EXPRESSION:
50/x+50/2x=1
50[(x)+(2x)]=(x)(2x)
150x=2x^2
2x^2-150x=0
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a=2 , b=-150, c= 0
x=%28150%2B-sqrt%2822500-4%282%29%280%29%29%29%2F%282%282%29%29
x=%28150%2B-sqrt%2822500%29%29%2F4%29 remove the negative sign
x=%28150%2Bsqrt%2822500%29%29%2F4%29
x=%28150%2B150%29%2F4
x=300%2F4
x=75
75(2)=150

Hence, the speed of one train is 75mph and for other its 150mph.
Paul.