Question

My friend sets out walking at 3 miles per hr. I set out behind her 5 minutes later at 4 miles per hour. For how many minutes will my friend have been walking when I catch up with her?

Answer 1

I think that you need to do 3*1/12=1/4 mile which is the distance between them after 5 minutes.

Answer 2

then time it takes for them to catch up by 1/4 mile is 12

Answer 3

is it not?

Answer 4

because every hour there is a disparity of 1 mile between them.

Answer 5

so for them to cover 1/4 mile they would need 1/4 hour .

Answer 6

60*1/4=15

Answer 7

yeah sorry about that it's I think 15min your thoughts?

Answer 8

Let d be the distance walked before catch up.
Time in minutes taken by friend at catch up = d/3 * 60
Time in minutes taken by me at catch up = d/4 + 5
Therefore equating the times we get
\[\large \frac{d}{3}\times60=\frac{d}{4}\times60+5\]
Now if you solve to find the value of d, you can plug the d value into d/3 * 60 to find the time to catch up in minutes.

Answer 9

Since the slower guy with 3 mile/per hour walked for 5 minutes, it's 3*1/12=1/4

Answer 10

d turns out to be 1 mile. Therefore the required time is 20 minutes.

Answer 11

@danyboy9169 Do you understand?

Answer 12

I don't think so

Answer 13

By the time 4 mile guy starts off there is a 1/4 mile distance

Answer 14

What part don't you understand?

Answer 15

because 5/12=1/12
1/12*3miles/hour=1/4 mile between them

Answer 16

we're using distance formula aren't we ?

Answer 17

It's physics

Answer 18

1/4mile to be covered with 1mile/h is of course it takes 1/4h

Answer 19

60*1/4=15min

Answer 20

Or if you taken the extra 5 min from the friend it will be 20min

Answer 21

is it not?

Answer 22

"Time in minutes taken by me at catch up = d/4 * 60 + 5"
Correction to my first post. The rest is correct.

Answer 23

might as well create a table
Friend - 3 mph (speed)
me - 4mph (speed) 5 minutes later so there's a delay

Answer 24

It's classical kinematics physics question

Answer 25

1 hour = 60 minutes.

Answer 26

You convert 5 min to hour.
5min*1hour/60min=

Answer 27

so we're solving for the distance

Answer 28

units "min" cancel out, leaving out the 1/12h.

Answer 29

mhm always remember those labels XD

Answer 30

Everything makes sense with units.

Answer 31

3mile/hour*1/12h=3/12mile(since h cancels out) or 1/4mile

Answer 32

There is 1/4mile between the friends

Answer 33

\[\large \frac{d}{3}\times60=\frac{d}{4}\times60+5\]
\[\frac{60d}{3}=\frac{60d}{4}+5\]
\[20d=15d+5\]
\[20d-15d=5\]
\[5d=5\]
\[d=1\]

Answer 34

4mile/hour-3mile/hour=difference of 1mile/hour

Answer 35

for 1 mile/hour to catch up for 1/4 mile

Answer 36

Let d be the distance walked before catch up.
Time in minutes taken by friend at catch up = d/3 * 60
Time in minutes taken by me at catch up = d/4 * 60 + 5 Therefore equating the times we get
\[\large \frac{d}{3}\times60=\frac{d}{4}\times60+5\]
which simplifies to
\[\large 20d=15d+5\]
therefore d = 1 mile
The time taken for the friend to walk 1 mile at 3 mph = 20 minutes.

Answer 37

d=1/4(miles)
v=1mile/h

Answer 38

so going back a bit if d = 1 then both sides would be 20
1 mile
20 minutes

Answer 39

Use the kinematics formula t=d
t=0.25mile/1mile/h=1/4h=15 minutes. Plus that 5 min for initial dilation.
15min+5min=20min

Answer 40

Use physics formula it's much easier

Answer 41

@Robert136
"Use the kinematics formula t=d"
A new one on me!!!!!!

Answer 42

:P nah prefer da mathz

Answer 43

How about
\[\large time=\frac{distance}{speed}\]

Answer 44

Yup

Answer 45

You can manipulate the formula without thinking much. Only the algebra skills required

Answer 46

yesssssssssssssssss @kropot72

Answer 47

So any missing value will be compensated by rearranging the formula

Answer 48

Got it, Since I walk 1 mile per hour faster than my friend, the distance between us shrinks at a rate of 1 mile per hour.

Since I am 1/4 mile behind when I start walking, it takes me 1/4 hour (= 15 minutes) to close the 1/4-mile gap.

At that time, my friend, who started 5 minutes before me, will have been walking for 5+15 =20 minutes.