Cars Leaving at Different Times

Date: 09/28/2003 at 18:39:43
From: Ryan
Subject: d=rt

Two cars leave a garage traveling in opposite directions. One car 
leaves at 8 am and averages 60 mph. The other car leaves at 9 am and 
averages 50 mph. At what time will they be 225 miles apart?

I realize that d = rt.  I know you have to add thee speeds so that you 
can divide it against the miles.  But all the examples in my book have
the cars leaving at the same time, not at different times.  I'm not
sure how to deal with that. 

Date: 09/28/2003 at 20:14:22
From: Doctor Terrel
Subject: Re: d=rt

Hi Ryan,

Yes, I know what you mean.  The problem wants you to "think out of 
the book".

Try this.  Let t = the time in hours traveled by the 2nd car.  Then
how long (or how many hours) does the first car travel?  When you know
that, you can use d = rt.

Or try another idea.  How far down the road is the first car BEFORE 
the 2nd car even starts?

Is that enough to get started? 

- Doctor Terrel, The Math Forum
  http://mathforum.org/dr.math/