SOLUTION: qmy drove to a friends house at a rate of 45mph. She returned by the same route at a rate of 50mph. The driving time for the round trip was 4hrs. what is the total distance amy tra

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Question 1164958: qmy drove to a friends house at a rate of 45mph. She returned by the same route at a rate of 50mph. The driving time for the round trip was 4hrs. what is the total distance amy travelled.
Found 3 solutions by Boreal, Alan3354, josgarithmetic:
Answer by Boreal(15235)   (Show Source):
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x hours to get there
4-x hours to get back
distance there is 45x miles
distance back is 50(4-x) miles
Those are equal
so 45x=200-50x
95x=200
x=2.105 hours to get there @45 mph=94.73 miles (rounded at end)
4-x=1.895 hours to get back @50 mph=94.73 miles
distance traveled was 189.46 miles

Answer by Alan3354(69443)   (Show Source):
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qmy drove to a friends house at a rate of 45mph. She returned by the same route at a rate of 50mph. The driving time for the round trip was 4hrs. what is the total distance amy travelled.
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Avg speed of the round trip = 2*45*50/(45+50) = 900/19 mi/hr
RT distance = r*t = (900/19)*4 = 3600/19 miles
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It's not possible to remember a formula for everything, but for a round trip:
Avg speed =
is similar to parallel work, parallel resistors, and easy to remember (IMO).

Answer by josgarithmetic(39620)   (Show Source):
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d, the distance in one direction OR the other direction.
t, time for returning

SPEED TIME DISTANCE GO 45 4-t d=45(4-t) BACK 50 t d=50t Total 4

Solve that for the time "back"

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