document.write( "Question 317832: In a family there are two cars. The sum of the average miles per gallon obtained by the two cars in a particular week is 35 . The first car has consumed 30 gallons during that week, and the second has consumed 40 gallons, for a total of 1200 miles driven by the two cars combined. What was the average gas mileage obtained by each of the two cars in that week? \n" ); document.write( "

Algebra.Com's Answer #227594 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
For each car, (miles driven)/(gallons consumed) = miles/gallon
\n" ); document.write( "Let $\"a\"$ = average miles driven by 1st car
\n" ); document.write( "Let $\"b\"$ = average miles driven by 2nd car
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"a+%2B+b+=+1200\"$ miles
\n" ); document.write( " $\"a%2F30+%2B+b%2F40+=+35\"$
\n" ); document.write( "Multiply both sides by $\"120\"$
\n" ); document.write( "(2) $\"4a+%2B+3b+=+4200\"$
\n" ); document.write( "Multiply both sides of (1) by $\"3\"$
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) $\"4a+%2B+3b+=+4200\"$
\n" ); document.write( "(1) $\"-3a+-+3b+=+-3600\"$
\n" ); document.write( " $\"a+=+600\"$
\n" ); document.write( " $\"b+=+1200+-+600\"$
\n" ); document.write( " $\"b+=+600\"$
\n" ); document.write( "The ave gas milage for $\"a\"$ is $\"600%2F30+=+20\"$ mi/gal
\n" ); document.write( "The ave gas milage for $\"b\"$ is $\"600%2F40+=+15\"$ mi/gal \n" ); document.write( "

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