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12 votes
12 votes
Two girls 21 miles apart. One going 3.5 mph one going 2.5 mph. How long until they meet up?

User CyberMonk
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1 Answer

13 votes
13 votes

From the picture,

x + y = 21

From definition,

speed = distance/time

The girl whose speed is 3.5 mph, walks x miles in t hours, that is:

3.5 = x/t

or

x = 3.5t

Similarly,

y = 2.5t

(they walk for the same time)

Replacing into the first equation:

3.5t + 2.5t = 21

6t = 21

t = 21/6

t = 3.5

It will take 3.5 hours until they meet up

Two girls 21 miles apart. One going 3.5 mph one going 2.5 mph. How long until they-example-1
User Harsh
by
3.2k points