SOLUTION: A hiker can walk at an average speed of 2 mph uphill and 6 mph downhill. Suppose he takes a hike on a mountain road which goes only uphill or downhill. What will be his average spe

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Question 252959: A hiker can walk at an average speed of 2 mph uphill and 6 mph downhill. Suppose he takes a hike on a mountain road which goes only uphill or downhill. What will be his average speed for such a trip, assuming he finishes at the level he started?
Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
We have to set up a RTD chart
hiker . . . . .rate . . . . .time . . . . . .distance
up . . . . . . .2 . . . . . . . d/2 . . . . . . . d
down . . . . .6 . . . . . . . d/6 . . . . . . . d
I assume he walks the same trail up and down, so that is the same distance.
time is distance / rate, so we have our 2 times.
we want average rate (speed). This is total distance over total time.
2d+%2F+%28d%2F2+%2B+d%2F6%29
adding the fractions, we get
2d+%2F+%284d%2F6%29
multiply by reciprocal, we get
12d%2F4d
His average rate is 3 mph