SOLUTION: a truck with a heavy load drove from boston to New york at a speed of 40 mph. After unloading, it returned from New york to boston at a speed of 60 mph. What was the average speed

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Question 1051684: a truck with a heavy load drove from boston to New york at a speed of 40 mph. After unloading, it returned from New york to boston at a speed of 60 mph. What was the average speed for the whole trip
Found 2 solutions by josmiceli, stanbon:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Average speed = [ total distance ] / [ total time ]
Let +d+ = the one-way distance Boston to NY
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Boston to NY:
+t%5B1%5D+=+d%2F40+
NY to Boston:
+t%5B2%5D+=+d%2F60+
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Average speed = +2d+%2F+%28+t%5B1%5D+%2B+t%5B2%5D+%29+
+2d+%2F+%28+d%2F40+%2B+d%2F60+%29+
+%28d%2Fd%29%2A%28+2%2F%28+1%2F40+%2B+1%2F60+%29%29+
Multiply top and bottom by +120+
+240+%2F+%28+3+%2B+2+%29+
+240%2F5+=+48+
the average speed is 48 mi/hr

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
a truck with a heavy load drove from boston to New york at a speed of 40 mph. After unloading, it returned from New york to boston at a speed of 60 mph. What was the average speed for the whole trip
B to NY DATA:
rate = 40 mph ; distance = x miles ; time = d/r = x/40 hrs
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NY to B DATA:
rate = 60 mph ; distance = x miles ; time = d/r = x/60 hrs
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Average speed = (total distance)/(total time) = 2x/(x/40 + x/60)
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= (2x)/(60x + 40x)/(40*60)
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= (2x)/[100x/2400]
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= 2/(1/24)
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= 48 mph
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Cheers
Stan H.
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