Find 10 of the same object (eg 10 stones or lego bricks). Using this 'whole-part model' below, ask the children to separate the 10 objects in different ways. Can they find all the ways to make 10? They could record them on paper in a number sentence,
ie: 1 +9 = 10. 2 + 8 = 10.
You could draw the whole-part model outside with chalk or in any way that you like. It's not necessary to use the one below.
If 10 isn't a challenge, you could have a go at 20. Can you see any similarities when comparing to the number bonds to 10?