SOLUTION: Find the speed of the train if an increase of 6kph lowers the time for a journey of 72km by 10 minutes. (Show Your Solution)

Question 394139: Find the speed of the train if an increase of 6kph lowers the time for a journey of 72km by 10 minutes. (Show Your Solution)
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Find the speed of the train if an increase of 6kph lowers the time for a journey of 72km by 10 minutes. (Show Your Solution)
..
let speed =x mph
increase speed = x+12
..
time = d/r
original time - increased speed time = 1/6 hours

..
LCD = x(x+12)

...

...
6*864=x^2+12x
5184=x^2+12
x^2+12x-5184 =0
solve using quadratic formula
a=1, b= 12,c=-5184
b^2-4ac=20880
you will get the speed = 66.24 kph
...
m.ananth@hotmail.ca

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