document.write( "Question 242908: A truck driver travels a certain distance at 60 miles per hour and returns over the same road at 40 miles per hour. What is her average rate for the round trip?\r
\n" ); document.write( "\n" ); document.write( "I know it is a d=rt but I don't know where to begin. Can Please help by explaining thoroughly. \n" ); document.write( "
Algebra.Com's Answer #177897 by Edwin McCravy(20054)\"\" \"About 
You can put this solution on YOUR website!
A truck driver travels a certain distance at 60 miles per hour and returns over the same road at 40 miles per hour. What is her average rate for the round trip?
\n" ); document.write( "I know it is a d=rt but I don't know where to begin. Can Please help by explaining thoroughly.
\n" ); document.write( "
\r\n" );
document.write( "\r\n" );
document.write( "Notice that you are NOT given the distance, but the distance will not\r\n" );
document.write( "matter, because the answer is independent of the distance.  However\r\n" );
document.write( "we have to let distance be a variable d anyway.\r\n" );
document.write( "\r\n" );
document.write( "Make this chart:\r\n" );
document.write( "\r\n" );
document.write( "             Distance      Rate       Time\r\n" );
document.write( "Going\r\n" );
document.write( "Returning\r\n" );
document.write( "---------------------------------------------\r\n" );
document.write( "Totals                     XXXX \r\n" );
document.write( "\r\n" );
document.write( "Fill in the distances, which are both d\r\n" );
document.write( "\r\n" );
document.write( "             Distance      Rate       Time\r\n" );
document.write( "Going           d            \r\n" );
document.write( "Returning       d          \r\n" );
document.write( "----------------------------------------------\r\n" );
document.write( "Totals                     XXXX                     \r\n" );
document.write( "\r\n" );
document.write( "Fill in their total 2d\r\n" );
document.write( "\r\n" );
document.write( "             Distance      Rate       Time\r\n" );
document.write( "Going           d           \r\n" );
document.write( "Returning       d          \r\n" );
document.write( "----------------------------------------------\r\n" );
document.write( "Totals         2d          XXXX     \r\n" );
document.write( "\r\n" );
document.write( "Fill in the rates, which are 60 and 40\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "             Distance      Rate       Time\r\n" );
document.write( "Going           d           60      \r\n" );
document.write( "Returning       d           40        \r\n" );
document.write( "----------------------------------------------\r\n" );
document.write( "Totals         2d          XXXX     \r\n" );
document.write( "\r\n" );
document.write( "Use the formula \"TIME=%28DISTANCE%29%2F%28RATE%29\" to fill\r\n" );
document.write( "in the times:\r\n" );
document.write( "\r\n" );
document.write( "             Distance      Rate       Time \r\n" );
document.write( "Going           d           60        d/60 \r\n" );
document.write( "Returning       d           40        d/40\r\n" );
document.write( "----------------------------------------------\r\n" );
document.write( "Totals         2d          XXXX       \r\n" );
document.write( "\r\n" );
document.write( "Total up the times\r\n" );
document.write( "\r\n" );
document.write( "             Distance      Rate       Time\r\n" );
document.write( "Going           d           60        d/60 \r\n" );
document.write( "Returning       d           40        d/40\r\n" );
document.write( "----------------------------------------------\r\n" );
document.write( "Totals         2d          XXXX     d/60 + d/40  \r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Now to calculate the average rate\r\n" );
document.write( "\r\n" );
document.write( "Average rate = \"%28total_distance%29%2F%28total_time%29+=+%282d%29%2F%28d%2F60%2Bd%2F40%29+\" \r\n" );
document.write( "\r\n" );
document.write( "To simplify that complex fraction, multiply top and bottom by 120:\r\n" );
document.write( "\r\n" );
document.write( "\"%282d%29%2F%28d%2F60%2Bd%2F40%29+\"\r\n" );
document.write( "\r\n" );
document.write( "\"%28120%2A2d%29%2F%28%28120d%29%2F60%2B%28120d%29%2F40%29+\"\r\n" );
document.write( "\r\n" );
document.write( "\"%28240d%29%2F%282d%2B3d%29\"\r\n" );
document.write( "\r\n" );
document.write( "\"240d%2F%285d%29\"\r\n" );
document.write( "\r\n" );
document.write( "\"%28240cross%28d%29%29%2F%285cross%28d%29%29\"\r\n" );
document.write( "\r\n" );
document.write( "See how the d's canceled?  That shows it didn't matter what the\r\n" );
document.write( "distance d was, and there is no way of finding out because it\r\n" );
document.write( "could be any number of miles.\r\n" );
document.write( "\r\n" );
document.write( "\"240%2F5\"\r\n" );
document.write( "\r\n" );
document.write( "\"48\"miles per hour.\r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" ); document.write( "
\n" );