SOLUTION: By driving 8 mph faster than Bob, John can make a 230 mile trip in one half hour less. How fast does Bob drive on the trip? Round your answer to the nearest mile per hour
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Question 599365: By driving 8 mph faster than Bob, John can make a 230 mile trip in one half hour less. How fast does Bob drive on the trip? Round your answer to the nearest mile per hour Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! By driving 8 mph faster than Bob, John can make a 230 mile trip in one half hour less.
How fast does Bob drive on the trip? Round your answer to the nearest mile per hour
:
Let s = Actual speed
then
(s+8) = faster speed
:
Write a time equation; time = dist/speed
:
Actual time - faster time = .5 hrs - = .5
:
multiply by s(s+8), results:
230(s+8) - 230s = .5s(s+8)
230s + 1840 - 230s = .5s^2 + 4s
;
Arrange as a quadratic equation
.5s^2 + 4s - 1840 = 0
:
Make the coefficient of s 1, mult by 2
s^2 + 8s - 3680 = 0
:
solve for s using the quadratic formula; a=1; b=8; c=-3680
I got a positive solution 56.8 mph
