In order to find the rate at which truck consumes fuel, calculate the slope of the given graph, by using the following formula:
where (x1,y1) and (x2,y2) are two points on the line.
Based on the given graph, you can select the points:
(x1,y1) = (0,500)
(x2,y2) = (500,200)
By replacing the previous values into the expression for m and simplifying you get:
The previous result means that the truck consumes its fuel at a rate of 0.6 liters/kilometer