document.write( "Question 420402: Burning Calories During strenuous exercise an athlete can burn 9 calories per minute on a stationary bicycle and 11.5 calories per minute on a stair climber. In a 30-minute workout an athlete burns 300 calories. How many minutes does the athlete spend on each type of exercise equipment? \n" ); document.write( "

Algebra.Com's Answer #293783 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"a\"$ = minutes spent on bicycle
\n" ); document.write( "Let $\"b\"$ = minutes spent on chair climber
\n" ); document.write( "---------
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"a+%2B+b+=+30\"$
\n" ); document.write( "(2) $\"+9a+%2B+11.5b+=+300+\"$
\n" ); document.write( "---------------------
\n" ); document.write( "(2) $\"90a+%2B+115b+=+3000\"$
\n" ); document.write( "(2) $\"+18a+%2B+23b+=+600+\"$
\n" ); document.write( "Multiply both sides of (1) by
\n" ); document.write( " $\"18\"$ and subtract (1) from (2)
\n" ); document.write( "(2) $\"+18a+%2B+23b+=+600+\"$
\n" ); document.write( "(1) $\"-18a+-+18b+=+540+\"$
\n" ); document.write( " $\"5b+=+60\"$
\n" ); document.write( " $\"b+=+12\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"a+%2B+b+=+30\"$
\n" ); document.write( " $\"a+=+30+-+12\"$
\n" ); document.write( " $\"a+=+18\"$
\n" ); document.write( "18 minutes on bicycle and 12 minutes on stair climber
\n" ); document.write( "check answer:
\n" ); document.write( "(2) $\"+9a+%2B+11.5b+=+300+\"$
\n" ); document.write( "(2) $\"+9%2A18+%2B+11.5%2A12+=+300+\"$
\n" ); document.write( " $\"+162+%2B+138+=+300\"$
\n" ); document.write( " $\"+300+=+300+\"$
\n" ); document.write( "OK \n" ); document.write( "

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