What strategy can be used to teach the 9s multiplication facts effectively?

The effective strategy for teaching the 9s multiplication facts involves utilizing the relationship between 10s multiplication facts and 9s multiplication facts. When you take a 10s multiplication fact, such as (10 \times 9) equaling 90, and then subtract the factor (which is 9 in this case), you can arrive at the answer for (9 \times 9). This means that (9 \times 9) is (90 - 9), yielding 81.

This method capitalizes on children's familiarity with the 10s facts, which are typically easier to memorize, and then introduces the concept of 9s in a relatable way. By using this approach, students can leverage their existing knowledge to solve the 9s multiplication facts more easily.

In contrast, while other strategies may have merit for different contexts or numbers, they don’t directly relate to the unique characteristics of 9s multiplication. For example, Turnaround Facts involve the idea that (a \times b = b \times a), which can be helpful in general multiplication but doesn’t specifically aid in memorizing 9s facts. Similarly, Doubling Twice or Increasing Place Value pertain to different multiplication strategies that