Stoke Minster CE (A) Primary School
Subtraction Policy
Mental and written calculation methods should be taught alongside each other throughout the entirety of this progression. When teaching children to calculate, emphasis
should be placed on choosing and using the method that is most efficient.
SUBTRACTION - YEAR 3 (Stage 3)
Expectations
Pupils should be taught to:

add and subtract numbers mentally, including:

a three-digit number and ones

a three-digit number and tens

a three-digit number and hundreds

add and subtract numbers with up to three digits,
using formal written methods of columnar
addition and subtraction

estimate the answer to a calculation and use
inverse operations to check answers

Solve problems, including missing number
problems, using number facts, place value, and
more complex addition and subtraction.
Vocabulary column subtraction, extended column subtraction, exchange, multibase/Dienes,decomposition, tens boundary
From KS1- subtract, take away, less than, minus, leave, how many are left/left over?, how many are gone?, one less, two less,
ten less…, how many fewer is… than…?, how much less is…?, distance between, difference between, equals, sign, is the same
as, inverse, partition, recombine, place value, tens, units/ones
Guidance & Written Methods for Subtraction
Pupils use their understanding of place value and partitioning, and practise using columnar addition and
subtraction with increasingly large numbers up to three digits to become fluent.
Written Methods
Steps:
1. extended column subtraction of 2 digit numbers using place value cards and multibase, without
decomposition see Year 2 (Stage 2)
2. before extended column subtraction needing decomposition children should be secure in partitioning 2
digit numbers in different ways e.g. 72 = 70 + 2 (using Dienes to support)
72 = 60 + 12
72 = 50 + 22
They can they practise the process of exchanging to show this partitioning and how it can be recorded.
72 =70 + 2
72 = 60 + 12
When this occurs, children should use the term ‘exchange’ to describe converting one ten into ten ones and
moving the ten units to the units columns column, leaving one less ten in the tens column.
3.
if need be, do jottings before extending column subtraction with decomposition- still use apparatus
Partition both numbers because you can’t subtract 2 from 1 partition again, then subtract, then recombine.
81
80
- 54
1 50
4
Partition again
70
11 50
4
1 - 4 can’t do
70 - 50 = 20
11 - 4 = 7
20 +
7 = 27
4.
Extending column subtraction with decomposition- still supported by place value cards, Dienes
Year 3 subtraction continued
Always begin with the least significant digits (on RHS)
working towards the most significant digits on LHS).
Use arrow cards to model partitioning,
and base 10 (Dienes) materials to model decomposition
of the number.
When solving 63 – 41, 41 does not exist as an amount
and therefore should not be represented by base 10
materials.
7
1
1
(80
+
5
4
(50
+
4)
2
7
20
+
7
8
-
70
10
1)
Set out vertically
Practical equipment e.g. subtraction cards and Dienes is used to secure an understanding of the formal written method.
5.
extended column addition of 2 digit numbers (as above) without the support of practical apparatus
6.
short method of column subtraction
7
8
-
7.
1
1
5
4
2
7
move to subtraction of 3 digit numbers , first without decomposition, then decomposition of tens
Example from New Curriculum Appendix
4
-
7
8
1
1
1
5
4
3
2
7