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Year 3 - Maths

Bridge 100 by adding in multiples of 10

Securing place value to 100 and applying to addition and subtraction

Unit Summary

In this unit pupils will use known facts to find multiples of ten that compose 100 and use known facts to find complements to 100. They will add and subtract multiples of ten, bridging 100.

Lesson Summary

You will learn to use number facts to 20 to add multiples of 10 and bridge 100.

Key Notes

  • The language of unitising helps us to use number facts to 20 to add multiples of 10 crossing the hundreds.
  • Crossing the tens boundary helps us to cross the 100s boundary if we think in tens.
  • Partitioning an addend helps us to cross the 100 boundary when adding.

Vocabulary To Learn

  • Addend: An addend means any of the numbers that are added together.
  • Bridging 100: Bridging 100 means partitioning one addend to make a number bond to 100 then adding the remaining part.

Common Mistakes To Avoid

  • Lack of fluency with number facts to 20 can hinder progress in applying them to multiples of ten.

3 Quick Questions (With Answers)

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

The language of unitising helps us to use number facts to 20 to add multiples of 10 crossing the hundreds. Crossing the tens boundary helps us to cross the 100s boundary if we think in tens.

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

An addend means any of the numbers that are added together. Use this word when showing your method, then check your final answer is reasonable.

3. Spot and fix this common maths mistake.

Mistake: Lack of fluency with number facts to 20 can hinder progress in applying them to multiples of ten. Correction: Ensure that fluency with number facts to 20 is secure or supported so that pupils can apply them.

More Lessons In This Unit

Browse all guides in the Year 3 Maths guide library.