document.write( "Question 490168: a car covers one -quarter of distance to the next town at 40km/hr,another quater at 50km/hr,and the rest at 90km/hr,find the car's average speed for the entire distance \n" ); document.write( "

Algebra.Com's Answer #333885 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
For average speed, always use (total distance) / (total time)
\n" ); document.write( "Let the entire distance = $\"d\"$ km
\n" ); document.write( "car's time for 1st $\"+d%2F4+\"$
\n" ); document.write( " $\"+t%5B1%5D+=+%28d%2F4%29%2F40+\"$
\n" ); document.write( " $\"+t%5B1%5D+=+d%2F160+\"$ hrs
\n" ); document.write( "car's time for 2nd $\"+d%2F4+\"$
\n" ); document.write( " $\"+t%5B2%5D+=+%28d%2F4%29%2F50+\"$
\n" ); document.write( " $\"+t%5B2%5D+=+d%2F200+\"$ hrs
\n" ); document.write( "car's time for last $\"+d%2F2+\"$
\n" ); document.write( " $\"+t%5B3%5D+=+%28d%2F2%29%2F90+\"$
\n" ); document.write( " $\"+t%5B3%5D+=+d%2F180+\"$ hrs
\n" ); document.write( "average speed = $\"+d+%2F+%28d%2F160+%2B+d%2F200+%2B+d%2F180%29+\"$
\n" ); document.write( "Divide top and bottom by $\"+d\"$
\n" ); document.write( "average speed = $\"+1+%2F+%281%2F160+%2B+1%2F200+%2B+1%2F180%29+\"$
\n" ); document.write( "Multiply top and bottom by $\"+20+\"$
\n" ); document.write( "average speed = $\"+20+%2F+%281%2F8+%2B+1%2F10+%2B+1%2F9%29+\"$
\n" ); document.write( "Multiply top and bottom by $\"360\"$
\n" ); document.write( "average speed = $\"+7200+%2F+%2845+%2B+36+%2B+40%29+\"$
\n" ); document.write( "average speed = $\"+7200+%2F+121+=+59.5+\"$ km/hr \n" ); document.write( "

\n" );