**Relating additions and subtractions to doubles **

**Teaching Point**

**Some prerequisite skills for being good at mental strategies for addition and subtraction are: doubling single-digit and two-digit numbers; adding and subtracting multiples of 5; making a number up to the next ten or next hundred by adding on. Focus on these in oral and mental lesson-starters.**

Using our facility for doubling with larger numbers could lead us to look at, for example, 36 + 37 and think ‘double 36 and 1 more’. Here are some more examples of how we might use our confidence with doubling and halving to get us started on some additions and subtractions:

48 + 46 could be related to double 46

46 + 46 = 92, so 48 + 46 = 92 + 2 = 94

62 + 59 could be related to double 60

60 + 60 = 120, so 62 + 59 = 120 + 2 – 1 = 121

54 – 28 could be related to half 54 (27) or double 28 (56)

54 – 27 = 27, so 54 – 28 = 27 – 1 = 26

56 – 28 = 28, so 54 – 28 = 28 – 2 = 26