document.write( "Question 641794: If Debbie can burn 200 calories in 20 minutes at a speed of 5 miles per hour, How long does it take Debbie to burn 200 calories at 4 miles per hour? \n" ); document.write( "
Algebra.Com's Answer #403824 by htmentor(1343)\"\" \"About 
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The \"burn\" rate, r, is 200 cal per 20 min per 5 mph:
\n" ); document.write( "r = 200 cal/(20 min * 5 mph) = 2 cal/mph*min
\n" ); document.write( "Inverting this gives (1/2)mph*min/cal
\n" ); document.write( "So it takes (1/2)*200 cal/4 mph = 25 min. to burn 200 cals at 4 mph
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