Addition and Subtraction with 2-Digit Numbers — Year 2 Lesson Plan
National Curriculum: Mathematics — Number: addition and subtraction using concrete objects, pictorial representations, and mentally — Year 2
Overview
Pupils learn to add and subtract 2-digit numbers using mental methods and informal written strategies. They build on place value knowledge to partition numbers and recombine, exploring methods such as partitioning, bridging through 10, and using number lines.
Learning Objectives
- Add two 2-digit numbers using partitioning or a number line.
- Subtract a 2-digit number from a 2-digit number using an appropriate strategy.
- Estimate answers before calculating using rounding to the nearest 10.
- Solve simple word problems involving addition and subtraction of 2-digit numbers.
Key Vocabulary
Suggested Lesson Structure
Rapid-fire: add multiples of 10 (30 + 40, 50 + 20) and subtract (80 − 30). Then add a single digit to a multiple of 10 (30 + 6, 50 + 8). Establish these as the building blocks.
Model partitioning to add: 34 + 23 → (30 + 20) + (4 + 3) = 50 + 7 = 57. Then model using a number line (jumping in tens then ones). Show subtraction by counting back on a number line and by partitioning the number being subtracted. Introduce bridging for cases like 37 + 8.
Pupils choose their preferred strategy (partitioning or number line) to solve a set of 2-digit additions and subtractions. Share methods: did different strategies give the same answer?
Pupils complete a set of additions and subtractions, then apply to two word problems. Challenge: find two 2-digit numbers that add to 75.
A calculation has been done incorrectly: 45 + 37 = 72. Can pupils spot the error and explain what went wrong?
Common Misconceptions
- Adding digits without considering place value: 34 + 23 = 57 but sometimes written as 5 + 7 = 57 (mixing digit addition with actual calculation).
- Subtracting the smaller digit from the larger regardless of position: 43 − 27, pupils may calculate 7 − 3 instead of exchanging — build this awareness before formal column method.
Prior Knowledge
Pupils should already be able to:
- Secure understanding of place value to 100.
- Fluency in addition and subtraction within 20.
- Ability to count in 10s from any number.
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