SOLUTION: A car traveled a distance of 100 miles. If its average speed had been 8 mph more, the trip would have taken 25 minutes less. What was the car's average speed? Please show me the st
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Question 912746: A car traveled a distance of 100 miles. If its average speed had been 8 mph more, the trip would have taken 25 minutes less. What was the car's average speed? Please show me the steps to solve this. Answer by mananth(16946) (Show Source):
You can put this solution on YOUR website! A car traveled a distance of 100 miles.
let speed be x mph
If its average speed had been 8 mph more, (x+8) mph
the trip would have taken 25 minutes less. =25/60 = 5/12 hours
Time with original speed - time with increased speed = 5/12
t=d/r
multiply equation by 12x(x+8)
12*100*(x+8) -12*100x = 5*x(x+8)
1200x+9600 -1200x = 5x^2+40x
5x^2+40x-9600=0
/5
x^2+8x-1920=0
x^2+8x+16 = 1920+16
(x+4)^2= 1936
x+4 = +/-44
ignore negative
x= 40 mph
