Year 2 - Maths
Calculate the difference
Calculating within 20
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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 add 3 addends. They will use a strategy such as finding 2 addends to total 10 or 2 numbers to bridge though 10.
Lesson Summary
You will learn to calculate the difference and find pairs that have the same difference.
Key Notes
- When comparing numbers, we can look at the difference between them.
- The difference between two numbers has a value.
- The difference can be shown as a bar model.
- Difference can be calculated as subtraction.
- Different pairs of numbers can have the same difference.
Vocabulary To Learn
- Difference: The result of subtracting one number from another. Way in which two or more things we are comparing are not the same.
- Same: Way in which two or more things we are comparing are like each other.
- Subtraction: To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.
Common Mistakes To Avoid
- Recording a subtraction to show difference incorrectly e.g. knowing that the difference between 4 and 6 is 2, but recording this as 4 - 6 = 2
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When comparing numbers, we can look at the difference between them. The difference between two numbers has a value.
2. Use this key word in a maths sentence and explain it clearly. 'Difference'
The result of subtracting one number from another. Way in which two or more things we are comparing are not the same. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Recording a subtraction to show difference incorrectly e.g. knowing that the difference between 4 and 6 is 2, but recording this as 4 - 6 = 2. Correction: Stress we can compare 6 to 4 or 4 to 6, but remind children that subtraction is not commutative so the whole (/ the larger number of those being compared) has to be written first in the expression. We can however change the position of the = symbol.
More Lessons In This Unit
- Add and subtract two numbers that bridge through 10 Study Guide
- Add three addends Study Guide
- Add three addends efficiently Study Guide
- Add three addends efficiently by finding two addends that total 10 Study Guide
- Add two numbers that bridge through 10 Study Guide
- Calculate the difference in different contexts Study Guide
- Calculate the difference when information is presented in a bar chart Study Guide
- Calculate the difference when information is presented in a pictogram Study Guide
- Compare the number of objects in two sets or difference between two measures. Study Guide
- Explain that the addends can be added in any order Study Guide
- Explain what the difference is between consecutive numbers Study Guide
- Use a 'First, then, then, now' story to add three addends Study Guide
- Use knowledge of calculating within 20 to solve problems Study Guide
- Use knowledge of calculating within 20 to solve problems involving statistics Study Guide
Browse all guides in the Year 2 Maths guide library.