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Question 118607: Sam drove a distance of of 410 miles in 7 hours. for the first part of the trip, his average speed was 40 mph and for the remainder of the trip, his average speed was 60 mph. how long did he travel at each speed?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Sam drove a distance of of 410 miles in 7 hours. for the first part of the trip, his average speed was 40 mph and for the remainder of the trip, his average speed was 60 mph. how long did he travel at each speed?
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1st part DATA:
Rate = 40 mph ; distance = "x" miles ; time = d/r = x/40 hrs.
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2nd part DATA:
Rate = 60 mph ; distance = "410-x" miles ; time = d/r = (410-x)/60
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EQUATION:
time + time = 7 hrs.
x/40 + (410-x)/60 = 7
Multiply thru by 120 to get:
3x + 2(410-x) = 7*120
3x + 820 - 2x = 840
x = 20 mles (distance traveled at 40 mph)
410-x = 390 (distance traveled at 60 mph)
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Cheers,
Stan H.
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