document.write( "Question 1016647: If car takes 30min to travel 10 miles,what is the speed of car in miles per hour?\r
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Algebra.Com's Answer #633035 by FrankM(1040) $\"\"$ $\"About$

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We have $\"10mi%2F30min\"$ and wish to convert to $\"mi%2Fhr\"$ \r
\n" ); document.write( "\n" ); document.write( "up top, the numerator, we are all set. To cancel min in the denominator, and replace with hours, we will multiply by $\"min%2Fhr\"$ but specifically $\"60min%2Fhr\"$ as that's the ratio between these units. \r
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\n" ); document.write( "\n" ); document.write( " $\"%2810mi%2F30min%29%2860min%2Fhr%29=%2820mi%2Fhr%29\"$ \r
\n" ); document.write( "\n" ); document.write( "Note, this process is called dimensional analysis, and can be used for a long chain of calculations. Say, feet/second to miles per year, for example. The setup is important because it keeps the units correct. Multiply by 1hr/60min above, by mistake, and you'll see minutes don't cancel, but you have hr^2 in the denominator. Pay attention to the units, and you won't make that mistake. \n" ); document.write( "

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