11.3.3 Decimal Coordinates
In the examples so far, all the coordinates were whole numbers and the scales were also marked at whole unit intervals. It is possible to plot points that have decimal coordinates such as (1.8, –2.1).
In the graph below, each unit along the axes has been divided into ten, so each gray line represents a tenth of a whole unit, or 0.1, just like on the number lines we saw in Unit 2. The point A has coordinates (1.3, 0.8) and is plotted 1.3 units across to the right of the origin and 0.8 units up.
Activity: Reading Decimal Coordinates
Write down the coordinates for the points B and C in the graph above.
B is plotted at the point which is 3 intervals to the left of the origin on the horizontal scale and 4 intervals past the 1 mark on the vertical scale, i.e. opposite –0.3 on the x-axis and opposite 1.4 on the y-axis. So the coordinates of B are (–0.3, 1.4).
Similarly, the coordinates of C are (–1.5, 0.9).
For more practice in plotting points, try the following pages: