SOLUTION: A person runs 3 miles and walks 2 miles. He runs twice as fast as he walks and finishes in exactly one hour. How fast does he walk. I am completely lost and not sure why. The book

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Question 243990: A person runs 3 miles and walks 2 miles. He runs twice as fast as he walks and finishes in exactly one hour. How fast does he walk.
I am completely lost and not sure why. The book gives simply the answer, 3.5 mph. I have:
r = d/t

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A person runs 3 miles and walks 2 miles.
He runs twice as fast as he walks and finishes in exactly one hour.
How fast does he walk.
:
let r = walking speed
then
2r = running speed
:
Write a time equation time = dist/rate
Walk time + run time = 1 hr
2%2Fr + 3%2F%282r%29 = 1
Multiply by 2r
2(2) + 3 = 2r
4 + 3 = 2r
r = 7%2F2
r = 3.5 mph walking rate
:
:
Check solution
2/3.5 + 3/7 = 1