document.write( "Question 1029799: Vinnie drives his car 120 miles and has a mean of a certain speed. If the mean speed had been 6 mph more, he could have traveled 136 miles in the same length of time. What was his mean speed? \n" ); document.write( "

Algebra.Com's Answer #644730 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+d+\"$ = distance in miles
\n" ); document.write( "Let $\"+r+\"$ = average rate in mi/hr
\n" ); document.write( "Let $\"+t+\"$ = time in hrs
\n" ); document.write( " $\"+d+=+r%2At+\"$
\n" ); document.write( " $\"+t+=+d%2Fr+\"$
\n" ); document.write( " $\"+t+=+120+%2F+r+\"$
\n" ); document.write( "----------------
\n" ); document.write( "also given:
\n" ); document.write( " $\"+t=+136+%2F+%28+r+%2B+6+%29+\"$
\n" ); document.write( "------------------
\n" ); document.write( "The times were the same, so
\n" ); document.write( " $\"+120%2Fr+=+136%2F%28+r+%2B+6+%29+\"$
\n" ); document.write( "Multiply both sides by $\"+r%2A%28+r+%2B+6+%29+\"$
\n" ); document.write( " $\"+120%2A%28+r+%2B+6+%29+=+136r+\"$
\n" ); document.write( " $\"+120r+%2B+720+=+136r+\"$
\n" ); document.write( " $\"+16r+=+720+\"$
\n" ); document.write( " $\"+r+=+45+\"$
\n" ); document.write( "The mean speed was 45 mi/hr
\n" ); document.write( "------------------
\n" ); document.write( "check:
\n" ); document.write( " $\"+t+=+120+%2F+r+\"$
\n" ); document.write( " $\"+t+=+120+%2F+45+\"$
\n" ); document.write( " $\"+t+=+2.667+\"$ hrs
\n" ); document.write( "and
\n" ); document.write( " $\"+t=+136+%2F+%28+r+%2B+6+%29+\"$
\n" ); document.write( " $\"+t=+136+%2F+%28+45+%2B+6+%29+\"$
\n" ); document.write( " $\"+t+=+136+%2F+51+\"$
\n" ); document.write( " $\"+t+=+2.667+\"$ hrs
\n" ); document.write( "OK \n" ); document.write( "

\n" );