#1369. The Number Nine

Mathematics, level: all
Posted Wed Oct 27 12:21:23 PDT 1999 by Barbara E. Walter (bewalt@hotmail.com).
Belmont Technical College, St. Clairsville, Ohio 43950
Materials Required: Chalkboard Colored Chalk
Activity Time: Approximately 1/2 Hour
Concepts Taught: Present students with non traditional method for multiplying the number NINE

OBJECTIVE

1. Reiterate the multiples of the number nine.
2. Relate to students another method for the multiplication of the number nine.
3. Present the method in such as way as to promote interest in the multiples of nine.

MOTIVATIONS

Use the chalkboard with various colors of chalk, to give attention to the workings of the multiples of nine, when following the multiples from 1 * 9 through 10 * 9.

DEVELOPMENT

1. Demonstrate the pattern s as they develop with the multiples.
· Begin with
· Answer is 9
· Remind students that the number 9 is the same as 09

2. Directly below 1 * 9 = 0 9
2 * 9 = ?
3. Begin explaining the pattern.
· The first pattern is on the left
The 0 increases one increment to 1 on the left.
· The second pattern in on the right
The 9 decreases one increment to 8 on the right
1 * 9 = 0 9
2 * 9 = u1 8v

4. Continue with the multiples from 3 * 9 through 10 * 9.
1 * 9 = 0 9
2 * 9 = u1 8v
3 * 9 = u2 7v
4 * 9 = u3 6v
5 * 9 = u4 5v
6 * 9 = u5 4v
7 * 9 = u6 3v
8 * 9 = u7 2v
9 * 9 = u8 1v
10 * 9 = u9 0v

SUMMARY

1. Now that left and right patterns have been demonstrated, Demonstrate that the results of the
multiples, when added together also result in the number 9.

1 * 9 = 0 9

2 * 9 = u1 8v 1 + 8 = 9

3 * 9 = u2 7v 2 + 7 = 9

4 * 9 = u3 6v 3 + 6 = 9

5 * 9 = u4 5v 4 + 5 = 9

6 * 9 = u5 4v 5 + 4 = 9

7 * 9 = u6 3v 6 + 3 = 9

8 * 9 = u7 2v 7 + 2 = 9

9 * 9 = u8 1v 8 + 1 = 9

10 * 9 = u9 0v 9 + 0 = 9

HOMEWORK

Assign various multiplication problems. Ask Student(s) to:
· Solve the problem
· Place the logic of how they solved the problem in writing
· Place any remaining questions they have on the multiples of 9 in writing on a separate sheet of paper.

PLEASE NOTE THAT THE u's should be up arrows on the left, and down arrows on the right.