To help you understand the algorithm, the video shows a simple two-digit by two-digit multiplication. You can see that the first and last digits are essentially the result of one multiplication.

Let’s revisit our example, 25 × 63, with efficiency in mind. In order to compute 25 × 63 using the standard algorithm, we had to perform four small multiplications: 3 × 5, 3 × 2, 6 × 5 and 6 × 2. The ...