SOLUTION: A car travels 910 miles at a certain speed. If the speed had been 5mph faster the trip would have been made 1hour less time. Find the speed?

Question 434379: A car travels 910 miles at a certain speed. If the speed had been 5mph faster the trip would have been made 1hour less time. Find the speed?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A car travels 910 miles at a certain speed.
If the speed had been 5mph faster the trip would have been made 1hour less time.
Find the speed?
:
Let s = actual speed
then
(s+5) = hypothetical faster speed
:
Write a time equation; time = dist/speed
:
Actual time - faster time = 1 hr
- = 1
Multiply equation by s(s+5), results:
910(s+5) - 910s = s(s+5)
:
910s + 4550 - 910s = s^2 + 5s
:
Combine to form a quadratic equation
0 = s^2 + 5s - 4550
You can solve this with the quadratic equation, but it will factor to:
(s + 70)(s - 65) = 0
The positive solution
s = 65 mph is the actual speed
:
:
See if that's true
910/65 - 910/70
14 - 13 = 1 hr

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