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Use multiplication:
31 x 11:
Line up our numbers vertically:
3 | 1 | |
x | 1 | 1 |
Current result: 1 x 1 = 1
3 | 1 | ||||
x | 1 | 1 | |||
1 |
Show value = 1
Current result: 1 x 3 = 3
3 | 1 | ||||
x | 1 | 1 | |||
3 | 1 |
Show value = 3
New multiplication row:
Insert a 0 as our placeholder
Current result: 1 x 1 = 1
3 | 1 | ||||
x | 1 | 1 | |||
3 | 1 | ||||
1 | 0 |
Show value = 1
Current result: 1 x 3 = 3
3 | 1 | ||||
x | 1 | 1 | |||
3 | 1 | ||||
3 | 1 | 0 |
Show value = 3
Add up our results by column:
3 | 1 | ||||
x | 1 | 1 | |||
3 | 1 | ||||
3 | 1 | 0 | |||
1 |
Adding up column 1, we get: 1 + 0
Our column sum becomes 1.
3 | 1 | ||||
x | 1 | 1 | |||
3 | 1 | ||||
3 | 1 | 0 | |||
4 | 1 |
Adding up column 2, we get: 3 + 1
Our column sum becomes 4.
3 | 1 | ||||
x | 1 | 1 | |||
3 | 1 | ||||
3 | 1 | 0 | |||
3 | 4 | 1 |
Adding up column 3, we get: 3
Our column sum becomes 3.