Lesson 4 of 19
Two dashes on one line
Show on a big screenA lift is on level 5. The parking area is on level −3. How many levels apart?
Step 1 of 3
- Start at 5.
- Take away −3.
- Two dashes turn the walk right. Land on 8.
From −3 to 0 is 3 levels. From 0 to 5 is 5 more. So they are 8 levels apart.
The gap is 5 − (−3). It has two dashes: the take-away sign and the minus of −3.
Rule: taking away a number below zero walks you right. The opposite of −3 is 3, so 5 − (−3) is 5 + 3. Adding 3 walks right.
| Written | Rewritten | Lands on |
|---|---|---|
| 5 − (−3) | 5 + 3 | 8 |
| (−2) − (−6) | (−2) + 6 | 4 |
| (−9) − (−4) | (−9) + 4 | −5 |
| 5 − 3 | 5 + (−3) | 2 |
Row three still ends below zero. Walking right does not always cross zero.
Slide the number taken away in the lab. Watch which way the walk goes.
Loading lab…
Try the lab to finish this lesson.