Mathematical+Reflections,+p+48

September 14th 2008

MR p48

1. Imagine a situation in which variable y depends on variable x (for example, y might be profit and x the number of items sold). If y increases as x increases, how would this be indicated in a table? In a graph?

In a table, this would be indicated by a rise in figures which are associated with y as figures associated with x increase. In a graph, this would be indicated by the graph going upwards from left to right, showing a rise in y as x increases.

2. If variable y decreases as variable x increases (for example, y might be the amount of money in your wallet on a trip and the time you have been traveling), how would this be indicated in a table? In a graph?

In a table, this would be indicated by a fall in figures in y, (which is the money) as x increases. which in this case is time you have been traveling. In a graph, this would be indicated by the shape of the graph by going down from left to right, as x increases.

3. In a coordinate graph of two related variables, when do points lie in a straight line?

In a coordinate graph, points lie in a straight line when there is a proportionate relationship between x and y.

4. In a coordinate graph of two related variables, when is it appropriate to connect the points?

It is appropriate to connect the lines when there is a relationship between x and y.