SOLUTION: a freight train makes a regular run of 1300km according to its schedule. the train dispatchers want to schedule this run for less than one hour, but the average speed will have to

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Question 401630: a freight train makes a regular run of 1300km according to its schedule. the train dispatchers want to schedule this run for less than one hour, but the average speed will have to be increased by 2km per hour. what average speed will be required to make the run on the new schedule?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
%281300%2Fr%29+-+%281300%2F%28r%2B2%29%29+%3C1
LCD = r(r+2)
%281300%28r%2B2%29-1300r%29%3Cr%28r%2B2%29
2600 r^2+2r-2600>0
r^2+52r-50r-2600>0
(r+52)(r-50)>0
r>50 the original speed
the rate has to be greater than 52 mph