# Year 4

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### We can explain each step when we write subtraction calculations in columns using the expanded method

##### Year 4 Unit 11c

#### What we are learning:

When children develop a column method of subtraction, it is important that they begin with a more expanded version of the traditional compact method. This, alongside some practical apparatus will allow them to develop an understanding of what they are doing

Try the example 388 – 257

First partition each number as follows:

Then try 354 – 283.

First partition each number as follows:

This method presents problems when you try to subtract 80 from 50.

However, changing the way we partition the numbers can be used to overcome this. We can partition 354 into 300 + 50 + 4 as shown above or as 200 + 150 + 4. By partitioning the numbers in this way we can solve the calculation.

#### Activities you can do at home:

Explore different subtractions using the expanded method, some where you can partition the top number easily, and some where you have to think of a different way to do it.

Keep talking about what you are doing, and the value of each digit in the numbers

Remember – there is no ‘borrowing’ in subtraction, we just partition the numbers in different ways so that we can subtract them.

#### Good questions to ask:

How are you going to partition this number?

Are there enough units, tens, hundreds etc in the top number to be able to subtract them like this?

If there are not – How else could you partition the number?

#### If your child:

Is not clear how to partition numbers in order to be able to subtract each column

Encourage them to think of different ways to partition a number, e.g. 287 can be partitioned in different ways:

200 + 80 + 7

200 + 70 + 17

100+ 180 + 7

100 + 70 + 17

##### Extension Activity

Please use this activity when you think your child understands the unit of work. It will deepen and extend your child’s understanding of this unit.