Question 71287
the jones family drove to Disneyland at 50mph and returned on the same route at 40mph.  Find the distance to Disneyland if the total driving time was 7.2hrs.
Distance(d)=rate(r)*time(t) -->d=rt
The distance to Disneyland is the same as the distance from Disneyland.
:
The rate to Disney is: 50mph
The time to disney is:t
Therefore the distance to Disney is: 50t
:
The rate from Disney is: 40mph
the time is the rest of the 7.2 hours of time not going to Disney: 7.2-t
Therefore, the distance from Disney is:40(7.2-t)
:
Since the two distances are equal:
50t=40(7.2-t)
50t=288-40t
50t+40t=288-40t+40t
90t=288
90t/90=288/90
t=3.2 hr
:
To find the distance, substitute t=3.2 into the distance to Disney equation of 50t:
d=50(3.2)=160 mi.
:
As a safety check, you can substitute t=3.2 into the distance from Disney equation and see if you still get 160:
d=40(7.2-3.2)
d=40(4)=160 mi.  It looks as if we're on the right track.
Happy Calculating!!!!