Calculation methods used in our school today.

A guide for Parents and Carers.

This is the way we do it (or at least some of the ways).

“They didn’t do it like that in my day!”

• Partitioning

• Chunking

• Number line

• Grid multiplication

Which is more important?

Mental Calculations

Or

Written Methods

When faced with a calculation, no matter how large or difficult the numbers may appear to be,

all children should ask themselves:

Can I do this in my head?

If I can’t do it wholly in my

head, what do I need to write

down in order to help me

calculate the answer?

Do I know the approximate size of the answer?

Will the written method I know

be helpful?

Addition

• On a whiteboard do this sum – 343 + 579

• In your head work out £3.99 added to £4.56.

• How did you do it?

Adding – Informal Methods86 + 57

86 136 140 143

+50

+4 +3

143

+7

Moving to a column method.

625 + 148

625

13

+ 148700 60

600 + 10020 + 40

5 + 8

773

625

700

148 13 60 20 + 40

5 + 8

773

600 + 100

Using a Standard Method

587 + 475

587 + 475

7 + 5 = 12Place the 2 in the units column

and carry the10 forward to the

tens column.

21

6011

80 + 70 = 150 then + 10 (carried forward) which totals 160.

Place the 60 in the tens column and carry the 100 forward to the hundreds column.

500 + 400 = 900 then + 100 which totals 1000. Place this in the thousands column

Subtraction

• On a whiteboard do this sum: 601 - 456

• In your head work out how much change you get from £20.00 if you spend £14.75.

• How did you do it?

Subtraction – Taking AwayHow do the number line and the column method link?

586 600 900 954590

+4 +10 +300 +54

954 - 586 Find the difference between the two numbers.Count on from 586 to 954.

954-586

368

10

54

4

300

Count onto the next multiple of 10

Count onto the next multiple of 100

Count onto the larger number

Count on in 100’s

To make 590

To make 600

To make 900

To make 954

Multiplication

• On a whiteboard do this sum: 45 x 15

• In your head work out how much you would spend if you bought 5 rolls of wallpaper at £16.99

• How did you do it?

Multiplication Using a Number Line.

14 x 510 x 5

1 x 5

1 x 5

1 x 5

1 x 5

70656055500

Grid Multiplication

• Partitioning

• Splits a number into its parts (makes it easy to see)

• E.g. 14 x 5 = (10 x 5) + (4 x 5)

14 x 5 (in a grid)

x

7020505

10 4

But can be done with “long multiplication”?

x

12

40 6

80

1200 1380

2

18030

46 x 32

92

1472

Expanded Method and Compact Method (you might recognise this one)

46X 321200

121472

80

(40 x 30)

(40 x 2)(6 x 2)

(6 x 30)180

46

1380(46 x 2)

X 32(46 x 30)

921472

Division• On a whiteboard do this sum: 640 divided by 12

• In your head work out how many 20cm pieces of ribbon you can get from a 2.4m roll.

• How did you do it?

Introducing division with a number line.

29 divided by 5

0 5 10 15 20 25 29

4 left over

5 groups of 5 with 4 left over5 r 4 This can also

be donebackwards.

Chunking on a Number Line

72 divided by 5

722220

5 x 10Subtract 10 groups

Of 5 from 72 to land on 22

5 x 4Subtract 4 groups

Of 5 from 22 to land on 2

14 groups of 5 subtracted together

R22 left!

This is the remainder

14 r2

Turning this into a column

72

22

2

0

5 x 10

5 x 4

r2 72 div 5 = 14 r2

Chunking256 divided by 7

256

0

4

186

46

116

7 x 10

7 x 10

7 x 10

7 x 6

r4

36 r4

-70

-42

-70186

116

46-70

4

7

7 x 6

7 x 10

7 x 10

7 x 10

Subtractchunks of70 (7 x 10)

How manyGroups of 7

in 46?

Total the numbers of groups of 710 + 10 + 10 + 6 = 36 r4

256-210

-4246

7

4

7 x 30

7 x 6

When comfortable with this then

move onto compact method

256