SOLUTION: a bridge in a state is 102 feet long. phil started walking across the bridge at the same time. heims speed was 5 feet per minute faster than phils. if heim finished walking across
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Question 851638: a bridge in a state is 102 feet long. phil started walking across the bridge at the same time. heims speed was 5 feet per minute faster than phils. if heim finished walking across the bridge 2 and 1/2 minutes before phil, find phils average speed per minute. Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! a bridge in a state is 102 feet long.
Phil started walking across the bridge, at the same time heim's speed was 5 feet per minute faster than phils.
if heim finished walking across the bridge 2 and 1/2 minutes before Phil, find Phils average speed per minute.
:
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Let s = Phil's walking speed in ft/min
then
(s+5) = Hiem's speed
:
Write a time equation; time = dist/speed
Phil's time - H's time = 2.5 min - = 2.5
multiply by s(s+5), cancel the denominators and you have:
102(s+5) - 102s = 2.5s(s+5)
102s + 510 - 102s = 2.5s^2 + 12.5s
A quadratic equation
2.5s^2 + 12.5s - 510 = 0
get rid of the decimals, multiply by 2;
5s^2 + 25s - 1020 = 0
You can use the quadratic formula here but this will factor to:
(5s - 60)(s + 17) = 0
5s = 60; positive solution is all we want here
s = 60/5
s = 12 ft/min is Phil's waking speed
:
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You can confirm this solution by finding the actual time of each
102/12 = 8.5 min
102/17 = 6 min
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time dif: 2.5 min
