Compatible Numbers

Using Materials

Problem: Tina has 6 tomatoes, Miriam has 2 tomatoes and Liam has 3 tomatoes. They use 9 tomatoes for a salad. How many tomatoes are left?

Discuss how to record the problem then record 6 + 2 + 3 - 9 on the board. The students model piles of 6, 2 and 3 counters. Discuss which two piles make 9 and remove them to leave 2. Record 2 on the board.

Examples: Word stories and recording for: 5 + 2 + 5 – 10, 9 + 5 +1 – 6, 8 + 2 + 7 – 9, 4 + 5 – 9, 3 + 5 + 5 – 8, 4 + 6 + 4 + 3 - 7….

Using Imaging

Examples: Word stories and recording for: 4 + 2 + 5 – 9, 8 + 5 + 2 – 7, 10 + 2 + 7  - 12, 10 + 5 – 15, 3 + 2 + 6 – 5, 2 + 6 + 4 + 3 - 7

Using Number Properties

Examples. Write these numbers on paper and cross out pairs and the numbers subtracted to get the answers: 8 + 6 + 4 – 10, 7 + 8 + 2 – 9, 7+ 3 + 3 + 7 - 10 – 10, 1 + 2 + 5 + 2 - 7 – 3, 9 + 6 + 4 - 7 - 2 ….