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In this activity, we will be finding the missing numbers in addition grids.
Look at this grid.
| + | 1 | 2 | 3 | 4 | 5 |
| 1 | |||||
| 2 | 6 | ||||
| 3 | |||||
| 4 | 6 | ||||
| 5 |
It shows that 2 + 4 = 6 and 4 + 2 = 6
Now look at this grid.
| + | 1 | 2 | 3 | 4 | 5 |
| 1 | |||||
| 2 | 3 | 6 | |||
| 3 | |||||
| 4 | 6 | ||||
| 5 | 9 |
It now also shows that 2 + 1 = 3 and 5 + 4 = 9
Example
Complete the grid below to find the value of A.
| + | 1 | 2 | 3 | 4 | 5 |
| 1 | 2 | A | 4 | 5 | 6 |
| 2 | A | 4 | 5 | 6 | 7 |
| 3 | 4 | 5 | 6 | 7 | 8 |
| 4 | 5 | 6 | 7 | 8 | 9 |
| 5 | 6 | 7 | 8 | 9 | 10 |
Answer
2 + 1 = 3 and 1 + 2 = 3
A is 3
| + | 1 | 2 | 3 | 4 | 5 |
| 1 | 2 | 3 | 4 | 5 | 6 |
| 2 | 3 | 4 | 5 | 6 | 7 |
| 3 | 4 | 5 | 6 | 7 | 8 |
| 4 | 5 | 6 | 7 | 8 | 9 |
| 5 | 6 | 7 | 8 | 9 | 10 |
Let's try some questions on this now.
