Addition Strategies: Using Doubles

Recall the doubles facts.

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

Add 4 and 5 using doubles plus one strategy.

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

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

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.