9er-Trick
| 9 = 10 - 1 |
1 • 9 = 10 - 1 = 1 mal 10 - 1 = 10 - 1 = 9
2 • 9 = 10 - 1 + 10 - 1 = 2 mal 10 - 2 = 20 - 2 = 18
3 • 9 = 10 - 1 + 10 - 1 + 10 - 1 = 3 mal 10 - 3 = 30 - 3 = 27
4 • 9 = 10 - 1 + 10 - 1 + 10 - 1 + 10 - 1 = 4 mal 10 - 4 = 40 - 4 = 36
5 • 9 = 10 - 1 + 10 - 1 + 10 - 1 + 10 - 1 + 10 - 1 = 5 mal 10 - 5 = 50 - 5 = 45
6 • 9 = 10 - 1 + 10 - 1 + 10 - 1 + 10 - 1 + 10 - 1 + 10 - 1 = 6 mal 10 - 6 = 60 - 6 = 54
usw.
Alles klar? => Also, nochmal:
1 • 9 = 1 mal 10 - 1 = 10 - 1 = 9
2 • 9 = 2 mal 10 - 2 = 20 - 2 = 18
3 • 9 = 3 mal 10 - 3 = 30 - 3 = 27
4 • 9 = 4 mal 10 - 4 = 40 - 4 = 36
5 • 9 = 5 mal 10 - 5 = 50 - 5 = 45
6 • 9 = 6 mal 10 - 6 = 60 - 6 = 54
7 • 9 = 7 mal 10 - 7 = 70 - 7 = 63
8 • 9 = 8 mal 10 - 8 = 80 - 8 = 72
9 • 9 = 9 mal 10 - 9 = 90 - 9 = 81
10 • 9 = 10 mal 10 - 10 = 100 - 10 = 90
Übung: ⇒ 9er-Trick
Beobachte, wie sich die Einer und die Zehner verändern:
| Z | E | ||
| ⇓ | 9 | ⇓ | |
| + 1 | 1 | 8 | - 1 |
| 2 | 7 | ||
| 3 | 6 | ||
| 4 | 5 | ||
| 5 | 4 | ||
| 6 | 3 | ||
| 7 | 2 | ||
| 8 | 1 | ||
| 9 | 0 |
