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Year 1 - Maths

Represent the inverse relationship between addition and subtraction

Additive structures: addition and subtraction

Unit Summary

In this unit pupils will find missing addends in equations. They will partition a whole into 2 parts representing first, then, now stories with subtraction equations. They will learn + and - are inverse operations.

Lesson Summary

You will learn to interpret and represent the inverse relationship between addition and subtraction.

Key Notes

  • Addition is the inverse of subtraction. Addition can 'undo' subtraction.
  • Subtraction is the inverse of addition. Subtraction can 'undo' addition.
  • When an amount is added to the start of a story, to 'undo' the change we must subtract the same amount.
  • When a given amount is subtracted from the start of a story, to 'undo' the change we must add the same amount.

Vocabulary To Learn

  • Add: o find the total, or sum, by combining two or more parts (addends), or to increase an amount by adding another.
  • Subtract: To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.
  • Inverse: Inverse means the opposite in effect; the reverse of.

Common Mistakes To Avoid

  • Children may look at the numbers but not be able to visualise the context, for example, they may try to undo 6 + 4 = 10 with 10 - 6 = 4

3 Quick Questions (With Answers)

1. Solve this in steps: explain the method from this lesson and why each step matters.

Addition is the inverse of subtraction. Addition can 'undo' subtraction. Subtraction is the inverse of addition. Subtraction can 'undo' addition.

2. Use this key word in a maths sentence and explain it clearly. 'Add'

o find the total, or sum, by combining two or more parts (addends), or to increase an amount by adding another. Use this word when showing your method, then check your final answer is reasonable.

3. Spot and fix this common maths mistake.

Mistake: Children may look at the numbers but not be able to visualise the context, for example, they may try to undo 6 + 4 = 10 with 10 - 6 = 4. Correction: Use practical equipment to illustrate the importance of the number added and subtracted being the same. Link equations to contexts ensuring that children are secure with what each part of an equation represents when linked to a story context.

More Lessons In This Unit

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