document.write( "Question 1056787: Jessie recently drove to visit her parents who live 756 miles away. On her way there her average speed was 21 miles per hour faster than on her way home (she ran into some bad weather). If Jessie spent a total of 21 hours driving, find the two rates. \n" ); document.write( "

Algebra.Com's Answer #671865 by MathTherapy(10555) $\"\"$ $\"About$

You can put this solution on YOUR website!
Jessie recently drove to visit her parents who live 756 miles away. On her way there her average speed was 21 miles per hour faster than on her way home (she ran into some bad weather). If Jessie spent a total of 21 hours driving, find the two rates.
\n" ); document.write( "

Let speed to the house be S
\n" );
document.write( "Then return-trip speed = S - 21
\n" );
document.write( "We then get the following TIME equation: 
\n" );
document.write( "756(S - 21) + 756S = 21S(S - 21) --- Multiplying by LCD, S(S - 21)
\n" );
document.write( " ---------- Dividing both sides by 21
\n" );
document.write( "
\n" );
document.write( "
\n" );
document.write( "
\n" );
document.write( "
\n" );
document.write( "S(S - 84) - 9(S - 84) = 0
\n" );
document.write( "(S - 84)(S - 9) = 0
\n" );
document.write( "S, or speed to the house =            OR           S = 9 (ignore)
\n" );
document.write( "Speed on return trip: 84 - 21, or  \n" );
document.write( "

\n" );