SUBTRACTION STRATEGIES
These are strategies that we are teaching the children during maths sessions. We are wanting to
expose them to many different strategies so that can have a go at using them and allowing
themselves to find the best one for them. Some of these strategies lend themselves to counting
the difference on the fingers to start with but the hope is that these strategies become more
mental. I hope the follow examples help and if there are any questions, feel free to ask.
Friends of 10/Commutative Law
7 + 3 =10
3 + 7 =10
10 – 3 =7
10 – 7 =3
60 + 40 = 100
40 + 60 = 100
100 – 40 =60
100 – 60 = 40
Friends of 10 is knowing the one digit numbers that add to 10 and able to recall them quickly.
Commutative Law is knowing the above and the relationship between numbers that are added
together and can be taken away. (also known as fact families)
Count Back
76 - 5 =
1
76
2
3
75
74
4
73
5
72
71
This strategy is generally used when they are taking away numbers that are less than 10. It is being
able to count back ‘x’ amount to find the answer. (Always counting the first number in their heads or
counting the amount of jumps they have done.)
Count Down
89-81=
This strategy is counting down from the largest number to get to the smaller number to work out
what the difference is. Key is to be able to count backwards by ones and being able to tell the
amount counted back not just the number they reached.
1
89
2
88
3
87
4
86
5
85
6
84
7
83
8
82
81
Count Up
Counting up is when the numbers are closer together and you are starting at the smaller number
and counting up to the other. The children need to make sure that they are again counting the
amount of jumps they are completing in the process.
99 – 87 =
1
87
2
88
3
89
4
90
5
91
6
92
7
93
8
94
9
95
10
96
11
97
12
98
99
Partitioning
Partitioning is breaking the number up and knowing what makes up the number. I have included the
following examples to help you.
64
–
51=
50
4 2 8
1
64 - 50= 14
14 - 1=13
400
20
-
1 1 6
8 - 100
10 6
400 – 100 = 300
20 – 10 = 10
8–6=2
300 + 10 + 2 = 312
64 – 51 = 13
428 – 116 = 312
Halving
We are wanting the children to know their basic doubles as this will help them be able to halve a
number. We have also taught partitioning prior to it as this will also help them.
Half of 64 =
Knowing that they are able to half 6 or 60 and half 4
Take 10/Take multiples of 10
We are trying to get the children to notice that when they are taking 10 or a multiple of 10 that it is
quite simple and you are looking at changing the number in the tens place.
97 – 10 = so knowing that as there is a zero in the number you are subtracting you are only looking
at changing the tens
97 – 10 = 87
85 – 30 = 55
80 -30 = 50 or 8 – 3 = 5