SOLUTION: Minh walked a total of 4 miles in 75 minutes. It he walked at 3.5 miles per hour for the first 30 minutes, what was his average speed for the rest of the time?

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Question 620599: Minh walked a total of 4 miles in 75 minutes. It he walked at 3.5 miles per hour for the first 30 minutes, what was his average speed for the rest of the time?
Found 2 solutions by rfer, ankor@dixie-net.com:
Answer by rfer(16322) (Show Source):
You can put this solution on YOUR website!
3.5/2=1.75
4-1.75=2.25
2.25/(35/60)=3.9 mph

Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
Minh walked a total of 4 miles in 75 minutes.
If he walked at 3.5 miles per hour for the first 30 minutes, what was his average speed for the rest of the time?
:
Convert 75 min to 1.25 hrs. and 30 min to .5 hrs
:
Let s = his speed the the last half mile
and
1.25 - .5 = .75 hrs = "the rest of the time"
:
Write a dist equation: dist = speed * time
:
3.5(.5) + .75s = 4
1.75 + .75s = 4
.75s = 4 - 1.75
.75s = 2.25
s = 2.25/.75
s = 3 mph his speed the last half mile
:
:
Check this by finding the total distance
3.5 * .5 = 1.75 mi
3.0 * .75 = 2.25
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total dist 4 mi