SOLUTION: a bridge in a state is 450 feet long. phil and heim started walking across the bridge at the same time. heim's speed was 2 feet per minute faster then phil's. if heim finished walk

Question 612588: a bridge in a state is 450 feet long. phil and heim started walking across the bridge at the same time. heim's speed was 2 feet per minute faster then phil's. if heim finished walking across the brdige 2.5 minutes before phil, find phil's average speed in feet per minute.
Phil's average speed is ___ feet per minute
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Let Phil's apeed be x ft/m
Heim's speed = x+2 ft/m
distance = 450 ft
time = distance/speed
time taken by Phil - time taken by Heim = 2.5
450/x - 450/(x+2)= 2.5
LCD = x(x+2)
multiply equation by LCD
450(x+2)-450x= 2.5x(x+2)
450x+900-450x=2.5x^2+5x
2.5x^2+5x-900=0
/2.5
x^2+2x-440=0
x^2+22x-20x-440=0
x(x+22)-20(x+22)=0
(x+22)(x-20)=0
x= 20 OR -22
speed cannot be negative. so phil's speed = 20ft/m

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