SOLUTION: A roller coaster goes down the first grade 8 times faster than it goes up the other side. The distance down is 100 ft. more than the distance up, and it takes 70 seconds to go up a
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Question 640662: A roller coaster goes down the first grade 8 times faster than it goes up the other side. The distance down is 100 ft. more than the distance up, and it takes 70 seconds to go up and 10 seconds to come down. What is the speed in ft. per second of the roller coaster when it goes up and when it comes down?
I've tried a proportion: and got and my teacher said the answer is not a decimal but the equation is an equality. Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! A roller coaster goes down the first grade 8 times faster than it goes up the other side.
The distance down is 100 ft. more than the distance up, and it takes 70
seconds to go up and 10 seconds to come down.
What is the speed in ft. per second of the roller coaster when it goes up
and when it comes down?
:
Let s = speed going up
then
8s = speed coming down
:
coming down equation (speed = dist/time) = 8s
solve for d
d + 100 = 80s
d = 80s - 100
:
and going up equation = s
d = 70s
:
d=d, therefore
80s - 100 = 70s
80s - 70s = 100
10s = 100
s = 10 ft/sec going up
then
8(10) = 80 ft/sec going down
:
:
Check this by finding the actual distances
Down: 10*80 = 800 ft
Up: 70 * 10 = 700 ft; a dif of 100'
