### Teaching and Group Activities for Understanding

**Day 1 Teaching**

Show a grid (see resources) and model adding two numbers using partitioning into 10s and 1s. Write 137 + 19, 178 + 31, 125 + 26, 154 + 27 and 22 + 195 on the board. Discuss how to do each one, using partitioning for all except the first, where adding 20 then subtracting 1 is best.

**Group Activities**Use the ‘Make 100’ in-depth problem-solving investigation below as today’s group activity.

Or, use these activities:

-- Create and add 3-digit and 2-digit numbers, investigating finding totals with different criteria.

**Day 2 Teaching**

Display 324 + 439. Children work in pairs and use the written method to find the answer on their whiteboards. Note/share different strategies. Explain that today we focus on compact written addition. Model this, emphasising leaving a space above the answer for writing extra numbers (‘carry’ digits).**Group Activities**

-- Add pairs of 3-digit numbers using compact written addition.

**Day 3 Teaching**

Display 592 + 235. Children use compact written addition on their whiteboards. Clarify any mistakes. Children then use this strategy to add three 3-digit numbers. Display:

1 | 2 | 3 | |||

4 | 7 | 4 | |||

+ | 3 | 3 | 2 | ||

Children calculate the total.

**Group Activities**

-- Create and add three 3-digit numbers using compact written additions.

-- Use compact written addition to add three 3-digit numbers with ‘carries’ in different columns.