What are doubles fact?
Double Facts are additions in which a number is added to itself. For example, 1 + 1, 2 + 2 etc. Internalizing double facts are helpful building blocks in developing fluency in adding single digit numbers.
What are doubles +1 facts?
Double Plus 1 Addition Facts
"Double plus one" facts are based on knowing doubles first, then just counting on one. This allows students to answer questions in which two adjacent numbers, such as 4 and 5, are added: Double 4 = 8, so 4 + 5 = 8 + 1 = 9.