SOLUTION: A car ia driving at 65 mph on a highway that follows railroad tracks. A train traveling 80 mph passes the car. How long after the train passes is it 20 miles ahead of the car? I

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Question 27201: A car ia driving at 65 mph on a highway that follows railroad tracks. A train traveling 80 mph passes the car. How long after the train passes is it 20 miles ahead of the car? I have no clue where to start on this one. Please help! Kat
Found 2 solutions by josmiceli, Paul:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You always have to read these carefully and sometimes restate them in a
way that makes it clearer.
the point where the train passes the car means they are dead even, neck and neck.
You start counting the time off there and you call the distance each has
travelled zero at that point.
The car can never catch up, let alone pass the faster train.
When is the slower car 20 miles behind the train?
distance = rate x time for both of them
d%5Bc%5D+=+r%5Bc%5D+%2A+t%5Bc%5D
d%5Bt%5D+=+r%5Bt%5D+%2A+t%5Bt%5D
r[c] = 65
r[t] = 80
You are going to put the same stopwatch on both train and car when the train
is 10 miles ahead, so t%5Bc%5D+=+t%5Bt%5D just call it t
d%5Bc%5D+=+65+%2A+t
d%5Bt%5D+=+80+%2A+t
The trains distance will be 20 miles ahead of the car's when you stop the time.
so d%5Bt%5D+=+d%5Bc%5D+%2B+20
d%5Bc%5D+%2B+20+=+80+%2A+t
substitute d%5Bc%5D+=+65+%2A+t for d[c] in the equation for the train's distaince.
65+%2A+t+%2B+20+=+80+%2A+t
15+%2A+t+=+20
t+=+1.3
1.3 hours is 1 hour and 20 minutes
You can check this answer by plugging it back into the equations
Use 4/3 for that
d%5Bc%5D+=+65+%2A+4%2F3
65+%2A+4%2F3+%2B+20+=+80+%2A+4%2F3
260%2F3+%2B+%283%2F3%29+%2A+20+=+320%2F3
260%2F3+%2B+60%2F3+=+320%2F3
320%2F3+=+320%2F3
it checks

Answer by Paul(988) About Me  (Show Source):
You can put this solution on YOUR website!
65x+80x=20
145x=20
x=20/145
x=4/29

Hence, after 4/29 hours the train is 20 miles ahead of the car.
Paul.