Alternative Method to Multiply When Multiplying by Nines

Method Overview00:00:00

The video introduces an alternative method for multiplying by nines (9, 99, 999, and so on). The core steps involve subtracting one from the first factor and then subtracting that difference from the second factor (the nines).

Example 1: Multiplying by 900:00:08

For 7 x 9, subtract 1 from 7 to get 6. Then, subtract 6 from 9 to get 3. Combining these results gives the product 63.

Example 2: Multiplying by 9900:00:22

For the second product, the video demonstrates the method for multiplying by 99. Subtracting one from the first factor yields 20, which is then subtracted from 99. The product is 2079.

Example 3: Multiplying by 99900:00:37

In the third example, for multiplying by 999, subtracting one from the first factor results in 784. Subtracting 784 from 999 gives 215, leading to the product 784215.