SOLUTION: By increasing her usual speed by 25 kilometers per hour, a bus driver decreases the time on a 25-kilometer trip by 5 minutes. Find the usual speed.

Question 916407: By increasing her usual speed by 25 kilometers per hour, a bus driver decreases the time on a 25-kilometer trip by 5 minutes. Find the usual speed.

Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Usual time - time after speed increase = 5 minutes
d= 25
let usual speed be x
increased speed = x+25
t=d/r
25/x-25/(x+25) = 5/60
25(x+25)-25x = 5x(x+25)/60
25x+625 -25x =(x^2+25x)/12
625 *12= x^2+25x
x^2+25x-7500=0
solve the quadratic equation
you should work it out
x= 75 km/h

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