SOLUTION: Jack and Jill went up the hill at a rate of 8 units per minute. They came tumbling down at a rate of 8 units per second. What was their average rate , in uni

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Question 497136:


Jack and Jill went up the hill at a rate of 8 units per minute. They came tumbling down at a rate of 8 units per second. What was their average rate , in units oer minute, for the round trip?


Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Jack and Jill went up the hill at a rate of 8 units per minute.
They came tumbling down at a rate of 8 units per second.
What was their average rate, in units per minute, for the round trip?
:
Find the tumbling down rate in units/min
8*60 = 480 units per minute
:
Let d = the one-way distance
Let a = average units/min for the round trip (2d)
:
Write a time equation; time = dist/rate
:
Up time + tumble down time = total time
d%2F8 + d%2F480 = %282d%29%2Fa
:
multiply by 480a, results
60ad + ad = 960d
61ad = 960d
we don't care about d, divide thru by d, to eliminate it.
61a = 960
a = 960%2F61
a = 15.738 units/minute average rate
:
:
Confirm this, let the one way dist = 1, find the times
1%2F8 + 1%2F480%29 = 2%2F15.738%29
use decimals here
.125 + .002 = .127, confirms our average speed of 15.738 units/min