Question

If a student can run the mile in 8 minutes, how many miles can they run in an hour?

Answer 1

The answer is:   "  7 $\frac{1}{2}$  $\frac{mi }{hr}$ "  ;

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    or, write as:  " 7. 5  $\frac{mi}{hr}$ " .

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Explanation:

To solve:

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Using a technique called "dimensional analysis" :

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  $\frac{1 mi}{8 min}$ * $\frac{60 min}{1 hr}$  ;

               =     $\frac{(1 * 60)}{(8 * 1 )}$   $\frac{mi}{hr}$

               =     $\frac{60}{8}$  $\frac{mi}{hr}$ ;

               =     $\frac{(60/4)}{(8/4)}$  $\frac{mi}{hr}$ ;

               =    $\frac{15}{2}$   $\frac{mi}{hr}$  ;

               =    { 15 ÷ 2 }  $\frac{mi}{hr}$

               =      "  7 $\frac{1}{2}$  $\frac{mi }{hr}$ " .  

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or, write as:     "  7. 5  $\frac{mi}{hr}$  " .

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