Addition Strategies by Making Ten

Let's find the number which should be added to 6 to make a 10.

6 + ? = 10

To find the required addend, let’s consider a model with 10 blocks and fill it with 6 balls.

Here, notice that we need four more balls to fill all the 10 blocks.
 

6 + 4 = 10
 

So, the required addend is 4.