### Teaching and Group Activities for Understanding

**Day 1 Teaching**Use a 20 bead frame to rehearse bonds to 10 and 20. Then use these facts to spot pairs to 10 and 20 when adding three numbers, e.g. 13 + 8 + 7 or 6 + 7 + 4. Encourage children to spot the bond to make the addition easy.

**Group Activities**

Use the in-depth problem-solving investigation ‘Getting the Balance’ from NRICH as today’s group activity. Or, use these activities:

**-- Children work in pairs to use number facts in adding three or four numbers less than 20.**

**Day 2 Teaching**

Write ■ + ▲ = 10 on f/chart. There are 2 mystery numbers here. What could they be? If square is 8, ask what triangle is? What if square was 1? So there are lots of possible answers. Repeat for different pairs of mystery numbers including subtraction: 20 - ■ - ▲ = 15.

**Group Activities**

-- Children learn how to find the mystery number in a number sentence using known number facts.