SOLUTION: It takes a car 2 hour less time than a truck to travel a 400 mile distance. Find the rate if each vehicle if the car travels 10 mph faster than the truck.

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Question 920003: It takes a car 2 hour less time than a truck to travel a 400 mile distance. Find the rate if each vehicle if the car travels 10 mph faster than the truck.

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
t = D/r
r the rate of the truck
400/r - 400/(r+10mph) = 2hr |Multiplying thru by r(r+10)so as all denominators = 1
400(r+10) - 400r = 2r(r+10)
2r^3 + 20r -4000 = 0
r^2 + 10r - 2000= 0 (Tossing out the negative solution for unit measure)
(r + 50)(r -40) = 0
r = +highlight_green%2840mph%29 , the rate of the truck. Car's rate is +highlight_green%2850mph%29 40%2B10
And...checking
400mi%2F%2840mph%29+-+400mi%2F%2850mph%29 = 10hr - 8hr = 2hr