You drove from your home to Dallas at an average spped of 60 mph and returned hom at an average speed of 45 mph. IF the total driving time was 21 hours, how far is it from your home to Dallas?
Hi cherubee,
From home to Dallas took t hours at 60mph.
From Dallas to home took 21 - t hours at 45mph.
The distances are the same, so let's find out how long it takes to drive to Dallas.
$\displaystyle 60t=45(21-t)$
$\displaystyle 60t=945-45t$
$\displaystyle t=9$
Distance = rate X time
So the distance from home to Dallas is 60(9) = 540 miles.