Mental Addition Strategies

Learning Objective

4Nc1: Derive quickly pairs of two-digit numbers with a total of 100

4Nc6: Add three or four small numbers, finding pairs that equal 10 or 20

Number Bonds to 100

72 + ? = 100 → Think: 72 + 8 = 80, then 80 + 20 = 100, so 72 + 28 = 100

Strategy: Make 10s First

When adding 7 + 8 + 3 + 2:

1. Find pairs that make 10: 7 + 3 = 10
2. Then: 8 + 2 = 10
3. Finally: 10 + 10 = 20

Video: Khan Academy (CC BY-NC-SA 4.0) | Aligned to Cambridge Primary 4Nc1, 4Nc6