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Year 1 - Maths

Understand subtraction as decreasing an amount

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 describe and interpret subtraction stories which involve decreasing an amount and write equations to represent this.

Key Notes

  • Decreasing the first amount in a story is a type of subtraction.
  • It can be represented as a 'First, then, now' story.
  • It can also be represented as an equation.
  • The first amount in a 'First, then, now' story must be written first in an equation.

Vocabulary To Learn

  • First: Before anything else.
  • Then: After something in time.
  • Now: At the present time.
  • Decrease: Make something smaller in size or quantity.

Common Mistakes To Avoid

  • Children may find the 'then' part of the story, where the amount changes, difficult to identify.

3 Quick Questions (With Answers)

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

Decreasing the first amount in a story is a type of subtraction. It can be represented as a 'First, then, now' story.

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

Before anything else. 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 find the 'then' part of the story, where the amount changes, difficult to identify. Correction: Draw attention to the change, talking about it as a decrease.

More Lessons In This Unit

Browse all guides in the Year 1 Maths guide library.