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      Understand why the order of addition and subtraction steps can be chosen

      I can understand why the order of addition and subtraction steps can be chosen.

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      Lesson 8 of 10
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      • Year 3

      Understand why the order of addition and subtraction steps can be chosen

      I can understand why the order of addition and subtraction steps can be chosen.

      Lesson details

      Key learning points

      1. Addition and subtraction can be done in any order
      2. If you do the addition and subtraction in a different order, the answer will be the same
      3. Problems can have equal answers even when different numbers are added and subtracted.

      Keywords

      • Reorder - Reorder means arrange something in a different way.

      Common misconception

      Pupils may reorder the numbers but forget to reorder the operations too.

      Model the problems using tens frames and number lines, ensuring that pupils understand that both the numbers and operations need to be reordered.

      In this session, pupils will learn that operations can be ordered in a calculation and the same answer is still reached (e.g. 11 + 5 - 3 = 11 - 3 + 5). The focus is not on getting the answer but on rearranging the problems. Tens frames and number lines can both be used to represent this concept.
      Teacher tip

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

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      6 Questions

      Q1.
      How can Izzy reorder this equation so it has the same value? 45 + 30 = 75

      Correct answer: 75 − 45 = 30
      Correct answer: 45 = 75 − 30
      35 + 40 = 75
      Correct answer: 30 = 75 − 45

      Q2.
      The equation 20 + 18 = 38 has been reordered in different ways. Match up the parts of the equations to make them correct.

      Correct Answer:20 =,38 − 18
      Correct Answer:18 = ,38 − 20
      Correct Answer:38 = ,18 + 20

      Q3.
      Find the missing part. 42 + $$\square$$ = 62

      Correct Answer: 20, twenty

      Q4.
      What is the missing number? $$\square$$ = 50 + 14

      Correct Answer: 64, sixty-four

      Q5.
      What is 12 + 4 + 4? =

      Correct Answer: 20, twenty

      Q6.
      Izzy and Lucas are collecting conkers. Izzy has 14 conkers and Lucas has 8 conkers. They find another 6 conkers. How many do they have altogether?

      Correct Answer: 28, twenty-eight

      Assessment exit quiz

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      6 Questions

      Q1.
      Which expression would give the same answer as 10 + 5 − 3?

      10 − 5 + 3
      12 − 3 + 5
      Correct answer: 10 − 3 + 5

      Q2.
      True or false? 11 + 1 – 3 is equal to 11 – 3 + 1

      Correct answer: true
      false

      Q3.
      True or false? 11 + 4 – 5 is equal to 11 – 2 + 1

      Correct answer: true
      false

      Q4.
      Match the expressions which have the same answer.

      Correct Answer:8 + 2 − 3,8 − 3 + 2
      Correct Answer:8 + 3 − 2,8 − 2 + 3
      Correct Answer:8 − 4 + 2 ,8 + 2 − 4

      Q5.
      There are 8 people on a bus. At the next stop, 3 people get on the bus and 4 people get off. How many people are on the bus? Which calculation would give the correct answer?

      8 − 3 + 4 =
      4 + 8 − 3 =
      Correct answer: 8 − 4 + 3 =
      8 + 4 − 3 =

      Q6.
      What step needs to be added to make this correct? 14 + 6 − 5 is equal to 14 − 5 ___

      Correct answer: + 6
      − 6
      + 5
      − 5

      Lesson appears in

      UnitMaths / Understand additive relationships and apply them to rearrange equations

      Maths

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