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 655239: 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 lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
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.
**
let x=usual speed
(x+25)=increased speed
travel time=distance/speed
5 min=5/60 hr=1/12 hr
..
25/x-25/(x+25)=5 min=1/12hr
LCD:x(x+25)
25(x+25)-25x=x(x+25)/12
25x+625-25x=(x^2+25x)/12
12*625=x^2+25x
7500=x^2+25x
x^2+25x-7500=0
(x+100)(x-75)=0
x=-100(reject)
or
x=75
usual speed of bus=75 mph
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