Multiplying by 9?

As a young student, I was required to learn the multiplication table beginning with 0 all the way to 12 x 12, which is 144.  As I teach my students each day, I am aware that there are some numbers in the multiplication table that are more difficult for them to learn than others.

Let's take a look at the number 9, and learn a basic trick.

9 x 1  =  09
9 x 2  =  18
9 x 3  =  27
9 x 4  =  36
9 x 5  =  45
9 x 6  =  54
9 x 7  =  63
9 x 8. =  72
9 x 9  =  81
9 x 10 = 90

Notice in the first column, containing all of the numbers highlighted in yellow, we begin counting with 0 and end with 9.  In the second column, highlighted in mauve, we begin with 9 and count down to 0.
Although the 0 in front of the 9 is absent mathematically in the first calculation of 9 x 1, I have included it for illustrative purposes.

That's the trick!  If you know someone who has difficulty mastering the multiplication of 9, please show them this practical tip!