SOLUTION: Imogene's car traveled 336 miles averaging a certain speed. If the car had gone 6 mph faster, the trip would have taken 1 hour less. Find the average speed.
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Question 903884: Imogene's car traveled 336 miles averaging a certain speed. If the car had gone 6 mph faster, the trip would have taken 1 hour less. Find the average speed.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Imogene's car traveled 336 miles averaging a certain speed.
If the car had gone 6 mph 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
:
normal speed time - faster speed time = 1 hr
- = 1
multiply equation by s(s+6), cancel the denominators and you have
336(s+6) - 336s = s(s+6)
336s + 2016 - 336s = s^2 + 6s
a quadratic equation
0 = s^2 + 6s - 2016
You can use the quadratic equation here, but this will factor to
(s-42)(s+48) = 0
the positive solution
s = 42 mph is the normal speed
:
:
Confirm this, find the actual time of each scenario
336/42 = 8 hrs
336/48 = 7 hrs
--------------
difference 1 hr
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