Year 5 - Maths
Use knowledge of column addition and subtraction to calculate with decimal numbers
Compose and calculate with decimals including column addition and subtraction
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will extend their understanding of formal calculation strategies to use column methods to add and subtract with decimal numbers.
Lesson Summary
You will learn to use knowledge of column addition and subtraction to calculate with decimal numbers.
Key Notes
- Numbers are recorded in columns with the same value digits in each column.
- Start with the smallest value column in case numbers need to be regrouped or exchanged.
- If the value of a digit in the minuend is greater than the same digit in the subtrahend, you will need to exchange.
- Make sure that any regrouped numbers are added in with others of the same value.
Vocabulary To Learn
- Decimal number: A decimal number has a decimal point followed by digits that show the fractional part.
- Regrouping: The process of unitising and exchanging between place values is known as regrouping. For example: ten ones can be regrouped for one ten.
- Place value: The value of a digit in a number based on where it is placed.
Common Mistakes To Avoid
- Pupils regroup incorrectly, particularly when subtracting e.g. exchanging one ten for ten ones.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Numbers are recorded in columns with the same value digits in each column. Start with the smallest value column in case numbers need to be regrouped or exchanged.
2. Use this key word in a maths sentence and explain it clearly. 'Decimal number'
A decimal number has a decimal point followed by digits that show the fractional part. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils regroup incorrectly, particularly when subtracting e.g. exchanging one ten for ten ones. Correction: Build the calculation using place value counters on a grid set out like a column method. Ask pupils to represent regrouping with counters.
More Lessons In This Unit
- Explain that decimal numbers with tenths can be composed additively Study Guide
- Explain that decimal numbers with tenths can be composed multiplicatively Study Guide
- Use known facts and mental strategies to calculate with decimal numbers within and across a whole Study Guide
- Use representations to round a decimal number with tenths to the nearest whole number Study Guide
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