SOLUTION: A boat traveled at 10 km/h for 1 hour, then at 13 km/h for 2 hours, and finally at 11 km/h for another hour... Over the whole trip the average speed was 15 km/h. How was it 15km/h

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A boat traveled at 10 km/h for 1 hour, then at 13 km/h for 2 hours, and finally at 11 km/h for another hour... Over the whole trip the average speed was 15 km/h. How was it 15km/h      Log On

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Question 899613: A boat traveled at 10 km/h for 1 hour, then at 13 km/h for 2 hours, and finally at 11 km/h for another hour... Over the whole trip the average speed was 15 km/h. How was it 15km/h
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The average speed is:
( total distance traveled ) / ( total time of travel )
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+d%5B1%5D+=+10%2A1+
+d%5B1%5D+=+10+ km
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+d%5B2%5D+=+13%2A2+
+d%5B2%5D+=+26+
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+d%5B3%5D+=+11%2A1+
+d%5B3%5D+=+11+ km
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+d%5B1%5D+%2B+d%5B2%5D+%2B+d%5B3%5D+=+10+%2B+26+%2B+11+
+d%5B1%5D+%2B+d%5B2%5D+%2B+d%5B3%5D+=+47+
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total time = +1+%2B+2+%2B+1+
total time = +4+ hrs
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+47+%2F+4+=+11.75+ km/hr
I don't see how it could be 15 km/hr
with the given numbers