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Addition Strategies: Using Doubles

Recall the doubles facts.

1 + 1 = 2 6 + 6 = 12
2 + 2 = 4 7 + 7 = 14
3 + 3 = 6 8 + 8 = 16
4 + 4 = 8 9 + 9 = 18
5 + 5 = 10 10 + 10 = 20

Let's find the numbers whose doubles can be used to add 4 and 5.

Add 4 and 5 using doubles plus one strategy.

1 a


4 + 5 = 4 + 4 + 1 = Double of 4 + 1 = 8 + 1 = 9
 

Now, let’s add 4 and 5 using doubles minus one strategy.
 

1 b

 

4 + 5 = 5 + 5 – 1 = Double of 5 – 1 = 10 – 1 = 9

So, doubles of 4 and 5 can be used to add 4 and 5.