Question

My friend sets out walking at a speed of $3$ miles per hour. 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 to her?

Answer 1

It would be about 8.75 minutes later so round that up to 9 minutes

Answer 2

Solution:

we are given that

My friend sets out walking at a speed of 3 miles per hour.

I set out behind her 5 minutes later at 4 miles per hour.

we have been asked to find

For how many minutes will my friend have been walking when I catch up to her?

Let the required time be t then we can write

As we know that $Distance=Speed*Time$

When they meet up then difference of distance traveled becomes zero.

so we can write

$4(t-5)-3t=0\\ \\ 4t-20-3t=0\\ \\ t=20$

Hence the required time is 20 minutes.