SOLUTION: After driving 126 miles, a person found that the drive would have taken 1 hour less time by increasing the speed by 8mph. What was the actual speed?
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Question 269786: After driving 126 miles, a person found that the drive would have taken 1 hour less time by increasing the speed by 8mph. What was the actual speed?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
After driving 126 miles, a person found that the drive would have taken 1 hour less time by increasing the speed by 8mph.
What was the actual speed?
:
Let s = actual driving speed
then
(s+8) = faster driving speed
:
Write time equation; time = dist/speed
:
Actual time - faster time = 1 hr
- = 1
multiply by s(s+8); results
:
126(s+8) - 126s = s(s+8)
126s + 1008 - 126s = s^2 + 8s
:
A quadratic equation
s^2 + 8s - 1008 = 0
:
Factors to
(s+36)(s-28) = 0
:
positive solution
s = 28 mph is the actual speed
;
:
Check solution (faster speed: 28+8=36)
126/28 - 126/36
4.5 - 3.5 = 1 hr
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