Plotting and interpreting graphs
_______________________________________________________________________________________________________________________

6. Linear graph with a gradient. Direct proportion

The variable shown on the y-axis changes its value in the same proportion as the variable shown on the x-axis does.

We can say that that variable A (distance in the graph) is directly proportional to B (time in the graph)

There are two possibilities in these types of graphs:

 Graph 1. The value of A is zero when the value of B is also 0. The equation for the relationship: A = kB


 Graph 2. The value of A is not 0 When the value of B is. The graph starts at the point (0, A0). A0 is the value of A when B is 0.
The equation for the relationship between A and B is: A = A0 + kB




A

L

C