Two numbers, and the order they come in
Show on a big screenA village map is ruled into squares. Each square stands for 100 metres. Where exactly is the well?
- Start at the origin, where both axes cross.
- Move 3 across.
- Move 4 up.
- Mark the point: (3, 4).
Try it first. Read the pair. Tap that spot on the grid.
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The rule
The well is where we start counting: 0 across, 0 up.
Two number lines cross at one point. One goes across, one goes up. Each is called an axis. That point is the origin, the zero of both scales. From the origin, count across, then count up. Two counts name one exact spot. Count in squares, not metres.
Write the pair in order: (across, up). This pair is the point's coordinates. The first number is the x-coordinate. The second is the y-coordinate.
Rule: The first number counts across. The second counts up. Swap them and the point changes, unless the two numbers match.
| Place | Across from the well | Up from the well | The pair |
|---|---|---|---|
| Well | 0 | 0 | (0, 0) |
| Pump | 3 | 4 | (3, 4) |
| School | 4 | 3 | (4, 3) |
| Bus stand | 6 | 0 | (6, 0) |
| Tank | 0 | 5 | (0, 5) |
A zero is a real count, not a missing one. The horizontal axis runs across. The vertical axis runs up. The bus stand sits on the horizontal axis. The tank sits on the vertical axis.
Try the lab to finish this lesson.