Stacking multiplications 1

Perhaps you already know the times table that covers multiplications with factors from 1 to 10. But as the factors grow larger, the number of products grows. Eventually, there are so many it’s simply impossible to learn them all by heart. And mental math with large numbers can quickly become pretty hard. So if we want to calculate, for example, 23 times 3, how do we do it?

We stack the factors, like this: The number with the most digits is on top. And the last digits in the numbers need to be in the same column. Not like this. Not like this. Like this.

This is the last column. We draw a line below the numbers. The stack is prepared. Now let’s calculate the product, digit by digit. We always start from the right.

3 times 3. These numbers are in the times table, and the result is 9. We write a nine below the line. The next calculation is three, from the lower row, times two, from the upper row. 3 times 2.

This is 6. We write a six in front of the nine. And there is the answer. 23 times 3 is 69. Let’s try another calculation.

12 times 4. We stack the numbers in the same way - we calculate with the help of stacking. 12 is the larger number, so we put it on top. 4 goes in the next row. Then, add the line.

Now let’s calculate, digit by digit. 4 times 2 is 8. 4 times 1 is 4. The product is: 48. But what if one of the factors contains three digits?

Does stacking work for even larger numbers? Yes, it does. Let’s calculate 212 times 4. We stack the numbers in the same way - write 212 above 4, and calculate digit by digit. 4 times 2 is 8.

4 times 1 is 4. And 4 times 2 again is 8. The product is: 848. This is how to multiply using stacking.