Use knowledge of column addition and subtraction to calculate with decimal numbers

I can use knowledge of column addition and subtraction to calculate with decimal numbers.

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Year 5

Use knowledge of column addition and subtraction to calculate with decimal numbers

I can use knowledge of column addition and subtraction to calculate with decimal numbers.

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Share activities with pupils

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Lesson details

Key learning points

Numbers are recorded in columns with the same value digits in each column.
Start with the smallest value column in case numbers need to be regrouped or exchanged.
If the value of a digit in the minuend is greater than the same digit in the subtrahend, you will need to exchange.
Make sure that any regrouped numbers are added in with others of the same value.

Keywords

Decimal number - A decimal number has a decimal point followed by digits that show the fractional part.
Regrouping - The process of unitising and exchanging between place values is known as regrouping. For example: ten ones can be regrouped for one ten.
Place value - The value of a digit in a number based on where it is placed.

Common misconception

Pupils regroup incorrectly, particularly when subtracting e.g. exchanging one ten for ten ones.

Build the calculation using place value counters on a grid set out like a column method. Ask pupils to represent regrouping with counters.

For worded problems, ask pupils to represent the problem as a bar model at first. This will help them to identify whether the wholes or parts are missing and whether they need to add or subtract.

Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).