document.write( "Question 561284: How far can a person drive out into the country at the average of 40 mph and returen over the same road at the average of 30 mph if the total travel time (out and back) is 7 hours? \n" ); document.write( "

Algebra.Com's Answer #364233 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+d+\"$ = distance into country in miles
\n" ); document.write( "Let $\"+t+\"$ = time to go into country in hrs
\n" ); document.write( "going in:
\n" ); document.write( "(1) $\"+d+=+40t+\"$
\n" ); document.write( "Coming back:
\n" ); document.write( "(2) $\"+d+=+30%2A%28+7+-+t+%29+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "(2) $\"+d+=+210+-+30t+\"$
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "(2) $\"+40t+=+210+-+30t+\"$
\n" ); document.write( "(2) $\"+70t+=+210+\"$
\n" ); document.write( "(2) $\"+t+=+3+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"+d+=+40t+\"$
\n" ); document.write( "(1) $\"+d+=+40%2A3+\"$
\n" ); document.write( "(1) $\"+d+=+120+\"$ mi
\n" ); document.write( "The person can go 120 mi into country
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+d+=+30%2A%28+7+-+t+%29+\"$
\n" ); document.write( "(2) $\"+120+=+30%2A%28+7+-+3+%29+\"$
\n" ); document.write( "(2) $\"+120+=+30%2A4+\"$
\n" ); document.write( "(2) $\"+120+=+120+\"$
\n" ); document.write( "OK \n" ); document.write( "

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