clix - Lesson 4: Post Parcel Charges

Activity 2: Finding the Charges Graphically

We can use the equations to plot graphs and predict find the charges graphically. This will enable us to find the charges very easily for different rates.

We can do this by plotting a graph of the equation

C = 8 × w + 30.

For doing this in GeoGebra we will write the equation as in the Input Bar at the bottom:

y = 8 × x + 30

To find the charges, we need to take points on this line. The value of x changes from 0 to 9. This is because if there are more than 9 units of 500gms., the weight will cross 5kg. and a different tariff rate will be applicable.

The animated gif below shows you how to do this.

To find the charges, we draw an intercept with a slider. The Y coordinate of the point of intersection of this intercept with our line gives us the required charges.

Similarly, for above 5 kgs, we can draw the graph for the equation:

C= (10 x w) + 102

Which is shown in this figure.

Above_5kg_graph

Above_5kg_Slider_movement

Moving the slider, we can know the value of charges required for that parcel. Here again the Y coordinate of the point of intersection gives us the charges applicable.

Thus, we see that drawing graphs is an easy way to find the charges for parcels.

geogebraicon (Click here to upload)

Try it on geogebra on your computer and upload the files here