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Year 1 - Maths

Know that addition and subtraction are inverse operations

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 recognise addition and subtraction as the inverse of each other.

Key Notes

  • Addition is the inverse of subtraction. Addition can 'undo' subtraction.
  • Subtraction is the inverse of addition. Subtraction can 'undo' addition.
  • When a given 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 not understand the importance of the order of the numerals in equations, so may not understand that the amount added or subtracted is of key importance when undoing a change made.

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 not understand the importance of the order of the numerals in equations, so may not understand that the amount added or subtracted is of key importance when undoing a change made. Correction: Present errors to discuss and correct. Encourage children to use practical equipment to demonstrate how they know they are right or to show why an error made cannot be correct.

More Lessons In This Unit

Browse all guides in the Year 1 Maths guide library.