Year 6

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We can add and subtract whole numbers and decimals using efficient written methods

Year 6 Unit 9

What we are learning:

  • Adding and subtracting decimals is straightforward as long as we remember to set the calculations out correctly.
  • When setting out an addition or subtraction that has decimal numbers in it, the decimal points must always sit vertically above/below one another, regardless of how many decimal places there are in each number.
  • Note how the decimal points always stay vertically in line with each other.
  • If we have 2.45 + 3.6 we therefore set it out like this. 

We can now complete the calculation and the decimal point will be in the right place in the answer. The same applies to subtraction.


Activities you can do at home:

Have a look at the worksheet together and try the calculations. The first skill is to set the calculations out correctly, ensuring that the numbers are in the correct columns. If the decimal points are aligned vertically this should be straightforward to achieve. Remember that if a number has no decimal, e.g. 3 this is the same as 3.0 or 3 units.

Good questions to ask:

Why do the decimal points have to be vertically in line with each other before we can complete the calculation?

If your child:

Sets out numbers in the wrong columns and the decimal points are not aligned vertically
Ask them to identify the value of each digit in each number so they can see that they have not aligned columns vertically, e.g. they may have tens and units in the same column which will not make sense when they try to add or
subtract or use a place value chart to help (see Unit 3)

Manages to set out additions and subtractions with two decimal places easily Give them calculations involving widely differing numbers of decimal places and ask them to align them ready for addition, e.g. 1345 + 1.345 + 0.1345 + 13450

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.


Extension activity (PDF)

Extension activity answers (PDF)