Module 3 Calculating
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Can I say a subtraction fact that is the inverse of an addition fact, and vice versa?

Example review questions

  • What is 14 − 8? How can we check this with addition?
  • Five is Empty box less than 12. How much greater is 12 than five?
  • What is the difference between 16 and 9? Write this as a subtraction calculation. What addition fact can you state from your number sentence?
  • 58 + 36 = 94
    Can you tell me two subtraction calculations that use the same numbers?
  • Empty box − 7 = 15
    Can you explain how you found the missing number?
  • On a number line, I start on 17, count back eight then count forwards eight. What number will I finish on? Can you draw a picture of what has happened?

Teaching guidance

This teaching guidance document suggests some of the key vocabulary, models, images and practical equipment that children should experience and be able to use. It also includes some teaching tips to provide a few starting points for ways of supporting children with this area of mathematics.

DOC file Can I say a subtraction fact that is the inverse of an addition fact, and vice versa? - teaching guidance | 103KB new window

Consolidation and practice

These resources are to support children in guided or independent work. Roll over the highlighted resources for a description.

PDF file How to use difference ITP | 159KB new window

SWF file Difference ITP | 40KB new window

PDF file How to use number line ITP | 182KB new window

SWF file Number line ITP | 47KB new window

XLS file Addition and subtraction number sentences | 96KB new window

XLS file Addition and subtraction facts | 62KB new window

DOC file 'I am thinking of a number' teaching prompts | 40KB new window

Difference

itp_difference.png

This interactive teaching program (ITP) is an ICT-based tool to support the exploration of number. Difference ITP allows the child or teacher to compare two rows of beads and to analyse the calculations they can represent. It can be used to promote the language of addition and subtraction. The ITP operates as a series of animations which show how the rows of beads can be represented by two number lines and then as a single number line with the difference indicated by a 'jump'.

Number line

itp_number_line.png

This interactive teaching program (ITP) is an ICT-based tool to support the exploration of number. Number line ITP allows the child or teacher to display a range of numbers from minus 50 up to 500. Children can estimate a number on the number line, explore the concept of difference between two given numbers and demonstrate their calculation strategies.

Opportunities to use and apply

Possible contexts include:

  • 'missing number' calculations, e.g. 18 − Empty box = 9,
    16 + Empty box = 30 − 8
  • checking calculations, e.g. Ella says that 25 − 7 = 16. What addition calculation can we use to check this?
  • number patterns and sequences, e.g. Find the missing numbers.
    A number sequence going up in increments of eight. There are six numbers. The sequence is blank, 35, 43, blank, 59, 67.
  • Number problems and puzzles, e.g. I think of a number, double it and add 11. I get the answer 17. What was my number?

Confirming learning

Use probing questions and prompts such as:

  • Eleven is three more than eight. Make a sentence using the same numbers and the words 'less than'.
  • Seven biscuits from a packet have been eaten. There are eight left. How many biscuits were in the packet?
  • The difference between 57 and 92 is 35. Write as many calculations as you can that use these three numbers.
  • 17 + 47 = 64
    Give three other calculations that use the same numbers.
  • Give me an example of when it would be useful to know an inverse fact.