document.write( "Question 1151347: Bus travels from Boston to New York 100km/h and back 80km/h. What was the average speed?
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Algebra.Com's Answer #773084 by greenestamps(13215) $\"\"$ $\"About$

You can put this solution on YOUR website!

\n" ); document.write( "The solution by tutor @MathLover1 is absolutely not right.

\n" ); document.write( "If equal TIMES are spent at two different speeds, then the average speed is the average of the two speeds.

\n" ); document.write( "But if equal DISTANCES are covered at two different speeds, more TIME will be spent at the lower speed, so the average speed for the round trip will be LESS THAN the average of the two speeds.

\n" ); document.write( "There are many correct ways to solve the problem; my preferred method is probably not a very common one. Here it is.

\n" ); document.write( "The ratio of the two speeds is 100:80 = 5:4.
\n" ); document.write( "Since the distances are the same, the ratio of times spent at the two speeds is 4:5.
\n" ); document.write( "Then the average speed is

\n" ); document.write( " $\"%284%28100%29%2B5%2880%29%29%2F%284%2B5%29=800%2F9\"$

\n" ); document.write( "or 88.9mph, to the nearest tenth.

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