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# Week 4 - 5 Addition and Subtraction

National curriculum content

• Add and subtract whole numbers with more than 4 digits, including using formal written methods (columnar addition and subtraction)
• Add and subtract numbers mentally with increasingly large numbers
• Use rounding to check answers to calculations and determine, in the context of a problem, levels of accuracy
• Solve addition and subtraction multi-step problems in contexts, deciding which operations and methods to use and why

Lesson objectives

1. Recap Add two 4-digit numbers - one exchange
2. Recap Add two 4-digit numbers - more than one exchange
3. Add whole numbers with more than 4 digits (column method)
4. Recap Subtract two 4-digit numbers - one exchange
5. Recap Subtract two 4-digit numbers - more than one exchange
6. Subtract whole numbers with more than 4 digits (column method)
7. Round to estimate and approximate
8. Inverse operations (addition and subtraction)
9. Multi-step addition and subtraction problems

What we want children to know

• When to choose a mental strategy or a standard method
• How to use their place value knowledge to confidently exchange in addition and subtraction calculations
• How to check calculations using rounding and estimating
• That calculations can be checked for accuracy using inverse operations
• How to select the key information from a word problem and use a bar model to support finding a solution

What skills we want children to develop

Use knowledge to solve Reasoning and Problem Solving questions such as:

True or False?

3999 – 2999 = 4000 – 3000

3999 – 2999 = 3000 – 2000

2741 – 1263 = 2742 – 1264

2741 + 1263 = 2742 + 1264

2741 – 1263 = 2731 – 1253

2741 – 1263 = 2742 – 1252

Convince me

Sam and Tom have £67·80 between them.

If Sam has £6·20 more than Tom, how much does Tom have?

1,235 people go on a school trip.

There are 1,179 children and 27 teachers. The rest are parents. How many parents are there?

Explain your method to a friend.

Always, sometimes, never

Is it always, sometimes or never true that the sum of four even numbers is divisible by 4?

Vocabulary/Mathematical Talk

• Why is it important to line the digits up correctly when we are adding numbers with different digits?
• Explain why we start in the lowest value place for addition and subtraction.
• In real life, when would we use an estimate?