Question 560076
I have word problems using d=r*t.  I need help with putting the numbers and variables in the right spots to make an equation.  After I figure out how to set up the equation, then I am able to solve the equation. 
I need help setting up the equation.

Here is the story problem.

A person can drive from town A to town B at a certain rate of speed in 5 hours.  If he increases his speed by 15kph, he can make the trip in 4 hours.  How far is it from town A to town B?        I made a table below but I'm not sure if everything is in the right spots.
<pre>
We are dealing with the two trips, (not "the two towns").  
One trip is at a slower speed and the other is at a faster speed.
Here is the chart you want to make:

                   Time   *   Speed   =   Distance
At slower speed              
At faster speed      
</pre>
>>...A person can drive from town A to town B at a certain rate of speed in 5 hours...<< <pre>
We let the first (slower) speed be S
We let the distance be D
We are given that the time is 5 hours, so we fill in the first line:

                   Time   *   Speed   =   Distance
At slower speed      5          S            D        
At faster speed     
</pre>
>>...If he increases his speed by 15kph, he can make the trip in 4 hours...<<
<pre>
To get the faster speed we add 15 kph to S, and that is S+15
The distance is the same, so it is still D
We are given that the time is 4, so we fill in the second line:

                   Time   *   Speed   =   Distance
At slower speed      5          S            D        
At faster speed      4         S+15   =      D

That gives us two equations in D and S:

                        5S = D
                   4(S+15) = D

Since both equal to D, they are equal to each other:

                        5S = 4(S+15)
                        5S = 4S + 60
                         S = 60

So his slower speed is 60 kph (and his faster speed is 15kph faster or 75kph)  

To find the distance we substitute 60 for S in  5S = D

                        5S = D
                     5(60) = D
                       300 = D                                    

Therefore the distance is 300 kilometers.

Edwin</pre>