<PRE><B>Question 811061</B>
a car traveled 252 miles averaging a certain speed if the car would have drove six miles per hour faster the trip would have taken 1 hour less
 find the average speed?
:
Let s = the average speed
then
(s+6) = the faster speed
:
Write a time equation; time = dist/speed
{{{252/s}}} - {{{252/((s+6))}}} = 1
multiply by s(s+6), resutlts
252(s+6) - 252s = s(s+6)
252s + 1512 - 252s = s^2 + 6s
Arrange as a quadratic equation on the right
0 = s^2 - 6s - 1512 = 0
This will factor to
(s+42)(s-36) = 0
the positive solution
s = 36 mph is the average speed
:
:
Check this by finding the time at each speed (fast speed = 42 mph)
252/36 = 7 hrs
252/42 = 6 hrs, one hr difference</PRE>