Subtraction

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

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

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

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

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

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.

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

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

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

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.

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

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

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

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 74 - 27 can be recorded by counting back 27 from 74 to reach 47. Partitioning needs to be used for this.

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

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.

Over to you! 59 - 13 (count up or back?) 86 – 68 (count up or back?) 142 - 35

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

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

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?)

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