SOLUTION: A boy covers 31km in 4 hours. He cycled part of the way at 14 km/h and he walked the rest of the way at 4 km/h. How far did he walk?

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Question 449501: A boy covers 31km in 4 hours. He cycled part of the way at 14 km/h and he walked the rest of the way at 4 km/h. How far did he walk?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A boy covers 31km in 4 hours.
He cycled part of the way at 14 km/h and he walked the rest of the way at 4 km/h.
How far did he walk
:
Let w = distance walked
then
(31-w) = distance biked
:
Write a time equation, time = dist/speed
:
Walk time + bike time = 4 hrs
w%2F4 + %28%2831-w%29%29%2F14 = 4
multiply by 28
28*w%2F4 + 28*%28%2831-w%29%29%2F14 = 28(4)
7w + 2(31-w) = 112
7w + 62 - 2w = 112
7w - 2w = 112 - 62
5w = 50
w = 50%2F5
w = 10 km walked
:
:
Check this by finding the actual times
10/4 = 2.5 hrs
21/14 =1.5 hrs
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total: 4 hrs