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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. Mental strategies
2. Add whole numbers with more than four digits
3. Subtract whole numbers with more than four digits
5. Inverse operations (addition and subtraction)
6. Multi-step addition and subtraction problems
7. Compare calculations
8. Find missing numbers

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?