Adding doubles is the same thing as multiplying by 2. Instead of memorizing the two tables, all you have to do is add the same number twice. Examples: 4*2=4+4=8, 7*2=7+7=14, etc.
Skip counting by 2's
If you add a number with itself it also equals to when you multiply a number by 2. Etc: 9+9=18 9*2=18. * = multiplication sign
