Speed Math Rules

02/12/2014

9x any single digit number >>

first number is 1 less than the original number,
last number is 9 less the first number:

9x2=18	9x3=27	9x4=36	9x5=45
9x6=54	9x7=63	9x8=72	9x9=81

8x any single digit number up to 5 >>

first number is 1 less than the original number,
last number is 8 minus twice the first number:

8x2=16

8x3=24

8x4=32

8x5=40

8x any single digit number more than 5 >>

first number is 2 less than the original number,
last number is twice the difference of 8 and the first number:

8x6=48

8x7=56

8x8=64

8x9=72

7x any even single digit number >>

last number is twice the original number,
first number is 1/2 the original number, plus the carry:

7x2=14

7x4=28

7x6=42

7x8=56

7x any odd single digit number >>

last number is twice the original number, plus 5,
first number is 1/2 the original number, plus the carry:

7x3=21

7x5=35

7x7=49

7x9=63

6x any even single digit number >>

last number is the same as the original number,
first number is 1/2 the original number:

6x2=12

6x4=24

6x6=36

6x8=48

6x any odd single digit number >>

last number is the same as the original plus 5,
first number is 1/2 the original number plus the carry:

6x3=18

6x5=30

6x7=42

6x9=54

5x any even single digit number >>

last number is always a 0,
first number is 1/2 the original number:

5x2=10

5x4=20

5x6=30

5x8=40

5x any odd single digit number >>

last number is always a 5,
first number is 1/2 the original number:

5x3=15

5x5=25

5x7=35

5x9=45

4x any single digit number >>

4x2=8	4x3=12	4x4=16	4x5=20
4x6=24	4x7=28	4x8=32	4x9=36

3x any single digit number >>

3x2=6	3x3=9	3x4=12	3x5=15
3x6=18	3x7=21	3x8=24	3x9=27