SOLUTION: If the average speed of a train was increased 10mph, the 300 mile trip it takes would require 1 hour less time. What is the new speed? I tried using the formula for distance: D

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Question 920200: If the average speed of a train was increased 10mph, the 300 mile trip it takes would require 1 hour less time. What is the new speed?
I tried using the formula for distance: Distance = rate x time
I used time = distance/ rate and got:
300/ x+10 = 300/x+10
but I don't think that works.
Thanks for helping.

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
t = D/r
300%2Fx+-+300%2F%28x%2B10%29+=+1hr |Multiplying thru by x(x+10)so as all denominators = 1
300(x+10) - 300x = 1x(x+10)
x^2 + 10x - 3000 = 0 (Tossing out the negative solution for unit measure)
(x+60)(x-50) = 0
x = 50mph. New Speed 60mph (50+10)
and...checking
6hr - 5hr = 1hr