Doubles and halves to 20
Recall doubles to 10 + 10 and matching halves.
Taught in Primary 2 in Nigeria (NERDC), Year 1 in United Kingdom (National Curriculum), Grade 2 in Canada (Ontario).
Nigeria (NERDC)
Primary 2
- Strand
- Basic Operations
- Called
- Doubles and halves to 20
- How it's taught
- Early move to vertical (column) arrangement with carrying and borrowing shown explicitly; drilled number facts.
United Kingdom (National Curriculum)
Year 1
- Strand
- Addition and Subtraction
- Called
- Doubles and halves to 20
- How it's taught
- Concrete–pictorial–abstract progression: bar models and number lines before formal columnar addition/subtraction with exchanging.
Canada (Ontario)
Grade 2
- Strand
- Number
- Called
- Doubles and halves to 20
- How it's taught
- Student-invented and mental strategies first (decomposing, compensating, open number lines); standard algorithms are consolidated later than in other systems.