Multiplication Rules

 

              Rule                                           Examples

 

0 Rule: anything times zero is zero                                  6 * 0 = 0

26 * 0 = 0

 

 

1 Rule: anything times 1 is itself                                        5 * 1 = 5

                                                                                                1 * 25 = 25

 

2 Rule: double the number or                                           6 * 2 = 12

          add it twice                                                                   2 * 5 = 10

 

4 Rule: double-double it                                                     4 * 3 = 12 (double 3

                                                                                             twice..3 doubled is 6,

                                                                                             so double that and you

                                                                                                get 12)

 

 

5 Rule: add by 5s                                                         3 * 5 = 5 + 5 + 5 = 15

                                                                                       5 * 4 = 5 + 5 + 5 + 5 = 20

 

 

9 Rule: Put your hands down flat, thumbs

between your hands.             

If multiplying by 7, put your 7th                                                                               6                                     3

finger down. That is a wall…count

the fingers on the left side of the wall,                                                                     7 * 9 = 63

that gives you the number in the tens

place. Count the fingers on the right

side of the wall, and that becomes

the number in the ones place.                                                  

 

 

10 Rule: just add a zero to the                              10 * 6 = 60

     end of the number                                   35 * 10 = 350

 

 

11 Rule:  just write the number                             8 * 11 = 88

twice (only works for                         4 * 11 = 44

numbers from 1 to 9)