Parents Guide to Parents Guide to SubtractionSubtraction

This Power Point Presentation will This Power Point Presentation will Show Parents the Language We Show Parents the Language We Use When Teaching Children Use When Teaching Children Subtraction Using Decomposition. Subtraction Using Decomposition.

Organising numbers:Organising numbers:

We organise numbers in columns We organise numbers in columns like this:like this:

HH T U T UHundreds Tens UnitsHundreds Tens Units

Only a single figure can go into Only a single figure can go into each column.each column.

Count up to 9Count up to 9

99 H T U

The units column is now full. You can only put one digit in each column. To make 10 we need to move to the next column.

The Tens ColumnThe Tens Column

3 3

00 H T U

We have 3 in the tens column and nothing in the units column. The number is 30.

The Hundreds ColumnThe Hundreds Column

3 3

00

00

H T U

We have 3 in the hundreds column and nothing in the tens or the units column. The number is 300.

Understanding Understanding Hundreds Tens and Hundreds Tens and

UnitsUnits33

11

99

H T UThe number

319 is:

3 hundreds

1 ten

9 units

How to Take AwayHow to Take Away

Make sure the biggest number is on Make sure the biggest number is on the top line.the top line.

305305

- 24- 24

------------------

How to Take AwayHow to Take Away

Begin in the Units Begin in the Units column.column.

Say:Say:

5 take away 4 is 15 take away 4 is 1

H T UH T U 3 0 53 0 5- 2 42 4------------------------ 11

How to Take AwayHow to Take Away

Move to the Tens Move to the Tens column.column.

Say:Say:

0 take away 20 take away 2

You have nothing – so You have nothing – so you can’t take away you can’t take away 2!2!

We need to EXCHANGE.We need to EXCHANGE.

H T UH T U 3 0 53 0 5- 2 42 4------------------------ 11

How to Take Away: How to Take Away: ExchangingExchangingYou have to take 1 You have to take 1

out of the out of the hundreds hundreds column.column.

H T UH T U 3 0 53 0 5- 2 42 4------------------------ 11

X 1 2

Now we have 2 hundreds and 10 Now we have 2 hundreds and 10 tens!tens!

Remember:

You are taking 100 out of the hundreds column. 100 is the same as 10 tens!

We Exchanged 1 We Exchanged 1 Hundred for 10 Hundred for 10

TensTensNow we say:Now we say:10 take away 2 is 810 take away 2 is 8

H T UH T U 3 0 53 0 5- 2 42 4------------------------ 11

X 12

Answer: 281Answer: 281

There is no digit below the 2 in the hundreds column so we say:

2 take away 0 is 2.

82

ExchangingExchanging

When the digit on the top line is smaller than the digit on the bottom line we say:

‘We need to exchange.’

One More ExampleOne More Example

H T UH T U

5 6 75 6 7- 3 2 9 3 2 9

------------------------

One More ExampleOne More Example

7 is smaller than 9.7 is smaller than 9.You have to take 1 You have to take 1

out of the tens out of the tens column.column.

H T UH T U 5 6 75 6 7

- 3 2 9 3 2 9 ------------------------ 88

X 1 5

Now we have 17 units and 5 tens!Now we have 17 units and 5 tens!

Remember:

You are taking 10 out of the tens column. So the 7 becomes 17.

One More ExampleOne More Example

Now we say:Now we say:5 take away 2 is 3.5 take away 2 is 3.

H T UH T U 5 6 75 6 7

- 3 2 9 3 2 9 ------------------------ 88

X 15

3

Move to the hundreds column.

Say:

5 take away 3 is 2.

Answer: 238 2

We hope this powerpoint will help We hope this powerpoint will help you to work with your child at you to work with your child at home.home.

Please ask in school if you have any Please ask in school if you have any questions regarding our approach questions regarding our approach to teaching maths.to teaching maths.

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