THE TEN COMMANMENTS OF MATHEMATICS

This is not written by me.. I was tagged in FB's note back in 2009.

And God said, "I am the Lord your God, who brought you out of arithmetic algebra, out of the land of Euclidean geometry:

1. Thou shall not divide by zero.
2. Thou shall not put other textbooks before thee in math class.
3. Thou shall show thy work; check thy work and confirm that thy results are reasonable.
4. Remember thy test days and prepare for them wholly.
5. Thou shall honor the correct order of operations.
6. Thou shall not do thy math homework in ink.
7. Thou shall commit the facts of arithmetic to memory.
8. Thou shall do unto one side of an equation what thou does to the other.
9. Thou shall not bear false witness against thy original problems; thou shall copy thy problems accurately and legibly.
10. Thou shall not covet thy neighbor's paper, not anything that is thy neighbor's."

When the people saw the derivatives and geometric constructions and heard the Linear Algebra students' torment, they trembled with fear. They stayed at a distance and said to Leibniz, "Speak to us yourself and we shall listen. But do not have the creator of Mathematics speak to us, lest the vast amount of information expand our minds so greatly such that our heads shall explode."

Easy way to memorize multiplication
====================================================

I introduced this method to my students, but it seem like not working! They still using their traditional method to find the answer.  For example, 2 x 8 = 2 + 2 + 2 + 2 + 2  + 2 + 2 + 2 = 16. Sadly, why they don't just add number 8 twice?! 2 x 8 = 8 x 2 = 8 + 8 = 16. Simple. They can't think of it. I don't blame them (I swear!).

I think 80% of math teachers knew this method. I will just share it again.

Multiplication of number 3 and 7

1.  Arrange the number as below:

         1         2          3
         4         5          6
         7         8          9

Multiplication of number 3:
                                                         start here     
                                                             \/
       2  1   <= 3x7     1  2    <= 3x4        3     <= 3x1
       2  4   <= 3x8     1  5    <= 3x5        6     <= 3x2
       2  7   <= 3x9     1  8    <= 3x6        9     <= 3x3

Multiplication of number 7:
                                                       
       2  1   <= 7x3     4  2     <=7x6      6   3     <= 7x9
       1  4   <= 7x2     3  5    <= 7x5      5   6     <= 7x8
           7   <= 7x1     2  8    <= 7x4      4   9     <= 7x7
           /\
     start here

Multiplication of number 9 (you can use your fingers too)

  Arrange number as below:
                    8    1        <= 9x9
                    7    2        <= 9x8
                    6    3        <= 9x7
                    5    4        <= 9x6
                    4    5        <= 9x5
                    3    6        <= 9x4
                    2    7        <= 9x3
                    1    8        <= 9x2
                          9        <= 9x1
                          /\

                     start here
 
To be continued..