Lesson 3 of 14
When two points share a coordinate
Show on a big screenTwo street lamps stand on the same side of a lane. How far apart are they?
Step 1 of 3
- One point: (2, 5).
- A second point, same row: (9, 5).
- Subtract: 9 − 2 = 7.
Step 1 of 3
- One point: (5, 1).
- A second point, same column: (5, 8).
- Subtract: 8 − 1 = 7.
Try it first. Slide the second point. Read the gap. Then switch between a row and a column.
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The rule
Two points sharing a coordinate lie on one row or column. A row runs across the grid. A column runs up it. To find how far apart they are, subtract the numbers that differ. Subtract the smaller number from the bigger one. A distance is never negative.
Take (2, 5) and (9, 5). Both share y = 5. Subtract: 9 − 2 = 7. The two points sit 7 units apart.
Take (5, 1) and (5, 8). Both share x = 5. Subtract: 8 − 1 = 7. The two points sit 7 units apart.
| The two points | Shared | Subtraction | Distance |
|---|---|---|---|
| (2, 5) and (9, 5) | y = 5 | 9 − 2 | 7 |
| (−3, 4) and (6, 4) | y = 4 | 6 − (−3) | 9 |
| (5, 1) and (5, 8) | x = 5 | 8 − 1 | 7 |
| (−2, −7) and (−2, 3) | x = −2 | 3 − (−7) | 10 |
From −3 to 0 is 3 units. From 0 to 6 is 6 units. So 6 − (−3) = 9, not 3.
Try the lab to finish this lesson.