The cost of coal is given by the formula Cost = 199.96 * Mass of coal + 100.00, reflecting direct proportionality with a slope of 199.96 and a y-intercept of 100.00.
From the graph, we can see that the cost of coal is directly proportional to the mass of coal, with a constant of proportionality (slope) of 200. This means that the formula for the cost of coal is:
Cost = 200 * Mass of coal + Cost against mass of coal
The cost against mass of coal is the y-intercept of the graph, which is 100. Therefore, the complete formula is:
Cost = 200 * Mass of coal + 100
To give the answer to 2 d.p., we can round the constants to 199.96 and 100.00, respectively. Therefore, the complete formula is:
Cost = 199.96 * Mass of coal + 100.00