Transcript Slide 1

Low Ash Primary School – Calculations policy
Addition Strategies:
Year 1
Counting on in 1s
7 + 6 = 13
0 1 2 3 4 5 6
7
8
9 10 11 12 13 14
Year 2
Counting on – partitioning into 10s and 1s
+ 10
23 + 12 = 35
23
33
Or
23 + 10 + 2 ->
23 + 10 = 33
then
+2
35
33 + 2 = 35
Counting on – adding nearly numbers - add 9, 11 by adding 10
and adjusting by 1.
+ 10
35 + 9 = 44
-1
35
44
35 + 11 = 46
+ 10
45
+1
35
45
Year 3
As Year 2 but with larger numbers. Extend adding near multiples
of 10 to a 2-digit number, e.g. 35 + 19.
46
Pencil and paper procedures.
83 + 42 = 125
83
+ 42
5
120
125
Year 4/5/6
Continue with number line methods
and pencil and paper procedures.
Extend adding nearly numbers
e.g. 125 + 59, 165 + 81,
143 + 4.9, 234 + 5.1
80 + 3
+ 40 + 2
120 + 5 = 125
Or
Refine column addition
- including
358
larger and
+ 73
decimal
431
numbers.
11
Low Ash Primary School – Calculations policy
Subtraction Strategies:
Year 1
Counting on/back in 1s
8 – 5 = 3 Find the difference
by counting on.
0 1 2 3 4 5 6
7
8
9 10
0 1 2 3 4 5 6
Year 2
Counting on – finding a difference (Extension)
7
8
9 10
9–2=7
Count back.
+1
42 – 39 = 3
+2
39
40
42
Subtracting nearly numbers – subtract a multiple of 10 then adjust.
- 10
35 – 9 = 26
+1
25
26
Counting back – partitioning into 10s and 1s.
24 – 13 = 11
-3
35
- 10
11
24
14
Year 3
As Year 2 but with larger numbers. Extend subtracting near
multiples of 10 to a 2-digit number, e.g. 35 - 19. Develop
complementary addition (counting on).
Year 4/5/6
Once a secure
Continue with number line methods for
potential
complementary addition, counting back and
level 5 - introduce
subtracting nearly numbers. Each year
decomposition.
numbers should get larger and include decimals.
6.1 – 0.4 = 5.7
5.7
Count back.
31
- 0.1
-0.3
6.0
6.1
+0.4
+0.8
6.8 – 5.6= 1.2
5.6
6.8
6.0
Count on.
546
- 318
228
Low Ash Primary School – Calculations policy
Multiplication Strategies:
Year 2
Arrays and repeated addition.
2 x 4 or 2 + 2 + 2 + 2 or 4 x 2
or
4+4 =8
0
1
2
3 4
5 6
7
8
Doubling – using partitioning (Extension)
15 x 2 = 30
10
+
5
Or
X2
20
+
3
90
Or
X
10
5
2
20
10
10 = 30
Year 3
As Year 2 – use arrays and repeated addition and use known facts
to carry out simple multiplications.
X 30
32 x 3 = 96
2
6
= 96
Year 4/5/6
Continue with the grid method – each
year numbers should get larger or
include decimals.
2.4 x 3.9 = 9.36
172 x 38 =6536
X 20
4
X 100 70 2
30 3000 2100 60
8 800 560 16
3800 2660 76
3800
2660
+ 76
6536
= 30
30 600 120
9 180 36
780 156
Treat as whole
780
numbers, then
+ 156
readjust accordingly 936
including a decimal
point.
After Year 6 Sats
introduce
standard method.
57
X 9
63 x units
450 x tens
513
Division Strategies:
Low Ash Primary School – Calculations policy
Year 2
Division as sharing and grouping.
Grouping - There are 6 sweets. How many people can have 2 each?
1
2
3
6 –: 2 = 3
0
2
4
6
Sharing – 6 sweets are shared between 2 people. How many do
they each have?
6 –: 2 = 3
Year 3
As Year 2 – continue grouping and sharing – with larger numbers.
Remainders.
1
2
3
4
5
16 –: 3 = 5 r1
0
3
6
15 16
9
12
Year 4
As Year 3. Extend to harder numbers and begin to write out
multiples.
10 x 4
10 x 4
4x4
96 –: 4 = 24
0
40
80
96
10 x 4
1. X 4 = 4
(40)
10 x 4
16
2. X 4 = 8
(80)
4x4
3. X 4 = 12 (120)
24 x 4
4. X 4 = 16 (160)
5. X 4 = 20 (200)
Year 5/6
6. X 4 = 24 (240)
0 3 2
As Year 4. Extend to
7. X 4 = 28 (280)
6 1 19 1 2
larger
numbers.
Year
8. X 4 = 32 (320)
Include
5 summer term
9. X 4 = 36 (360)
questions
onwards – children
10. X 4 = 40 (400)
with
secure with number
Use the dot to represent
remainder
line and secure
a zero to make it a
and
potential level 5’s
multiple of 10
decimal
can move on to short
answers.
division.
Can reduce to 1, 2, 4, 5, 10 x