The two apart facts are also called Doubles +2, Monkey in the Middle, or Robin Hood Facts.
A fact like 7 + 9 can be thought of as ‘Double 7, + 2 more’. This strategy relies on knowing the doubles and the near number +2.
The monkey in the middle naming comes from the idea that any two addends two apart can be found by doubling the middle number. For example, 7 + 9 is double 8.
Robin Hood is much the same, and refers to robbing from the ‘rich’ or higher number, and giving to the ‘poor’, or lower number.
For 7 + 9, take one from the 9 to give to the 7, and the question turns into 8 + 8.
|Robin Hood Flash CardsThese cards show the addition fact on two ten frames, with an arrow indicating how the fact can be made into a double.|