1. Subtraction

2. Mental Strategies for Subtraction
Secure mental subtraction requires the ability to:
recall key subtraction facts instantly (inverse of number pairs to 10, 20 & 100, halves etc) and to apply these to similar calculations
mentally subtract combinations of one and two digit numbers
understand that subtraction is the inverse of addition and recognise that subtraction can’t be done in any order (it has to start with the larger number)
understand the language of subtraction including less, minus, take away, difference between etc

3. Developing a maths concept
Abstract
‘Just do it’
Visualise
‘With eyes closed’
Visual
‘With eyes open’
Language
The importance of a practical approach initially and establishing understanding of associated mathematical language.
Concrete
Using objects 3

4. Counting Sets
This focuses on extending children’s counting skills to enable them to count up to ten objects accurately, in any arrangement.
The early stages of addition and subtraction are developed as children begin to partition and combine sets and to remove objects from sets

5. Foundation- Counting sets
Take away using different objects and materials
Find one less than a number from 1-10
Recognize that the number of objects in a set stays the same even if they are moved around

6. Counting sets
This phase focuses on the development of children’s early awareness of quantity.
less
more

7. Foundation Number words and numerals
Count backwards within 1-20
Say the number that comes before a given number
Recognize and continue patterns linked to number.

8. Year 1 Understanding subtraction
Taking away- removing objects
Difference- comparing and how many more is needed
Vocabulary- minus, less than, equals, same as, pattern

9. Year 1 Mental calculations
Recall and use subtraction facts to 10 fluently
Know number pairs with a total of 20 and derive related subtraction facts

10. Year 1 Mental methods and jottings
Subtract one digit and two digit numbers to 20
Partition a given number of objects(up to 20) into 2 groups

11. Year 1 Using a number line
Subtracting 18 – 4 =
Step 1: start on the biggest number and count back in jumps.
If the numbers are closer together it may be easier to count up.

12. Year 1 and Year 2 Written Calculations
No formal written layout
Encouraged to use jottings, pictures, number lines and mathematical statements.

13. Year 2 Understanding Subtraction
Partition a set
Understand subtraction of one number from another cannot be done in any order
Recognize the inverse relationship between addition and subtraction
Make generalizations

14. Year 2 Mental calculations
Recall and use subtraction facts to 20 fluently, and derive and use related facts up to 100.
Know complements to the next multiple of 10 e.g
Know pairs of multiples of 10 with a total of 100 and derive related subtraction facts.
52+?=60

15. Year 2 Mental methods and jottings
Stage 1: The empty number line
The empty number line helps to record the steps in mental subtraction. There are several ways to do this:
Counting Back - a calculation like can be recorded by counting back 27 from 74 to reach 47.
Partitioning needs to be used for this.

16. Year 2
Counting Up - the steps can also be recorded by counting up from the smaller number to find the difference

17. Written methods for Subtraction
Stage 1: The empty number line
With practice, children will need to record less information and decide whether to count back or forward.
It is useful to ask children whether counting up or back is the more efficient.

18. Over to you! 59 - 13 (count up or back?) 86 – 68 (count up or back?)

19. Y2 Subtraction a with number square
Subtracting 12
64 -12= 52
Subtracting 10 up 1
Subtracting 2 go left 2

20. Y2 Subtraction with a number square
Subtracting 9:
25 – 9 = 16
Subtract 10
Add 1

21. Keep maths practical and have fun!
Bath-time (filling and emptying containers, counting)
Counting rhymes
Talk about numbers in the environment (eg, front door numbers, number plates, road signs etc)
Help with the cooking (measuring, weighing, ordering the recipe)
Setting table places (how many plates/cups etc)
Paying in shops (including change)
Estimating amounts (how many apples/sweets?)

22. Thank you!