 # 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).

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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 Methods 86 + 57 86 136140143 +50 +4 +3 143 +7

Moving to a column method. 625 + 148 625 13 + 148 700 60 600 + 100 20 + 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 = 12 Place the 2 in the units column and carry the 10 forward to the tens column. 2 1 601 1 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 Away How do the number line and the column method link? 586600900954 590 +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 5 10 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 70 20505 10 4

But can be done with “long multiplication”? x 12 406 80 1200 1380 2 180 30 46 x 32 92 1472

Expanded Method and Compact Method (you might recognise this one) 46 X 32 1200 12 1472 80 (40 x 30) (40 x 2) (6 x 2) (6 x 30) 180 46 1380 (46 x 2) X 32 (46 x 30) 92 1472

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 05 1015202529 4 left over 5 groups of 5 with 4 left over 5 r 4 This can also be done backwards.

Chunking on a Number Line 72 divided by 5 722220 5 x 10 Subtract 10 groups Of 5 from 72 to land on 22 5 x 4 Subtract 4 groups Of 5 from 22 to land on 2 14 groups of 5 subtracted together R2 2 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

Chunking 256 divided by 7 256 0 4 186 46 116 7 x 10 7 x 6 r4 36 r4 -70 -42 -70 186 116 46 -70 4 7 7 x 6 7 x 10 Subtract chunks of 70 (7 x 10) How many Groups of 7 in 46? Total the numbers of groups of 7 10 + 10 + 10 + 6 = 36 r4 256 -210 -42 46 7 4 7 x 30 7 x 6 When comfortable with this then move onto compact method 256

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