Overview of calculator skills in Years 4, 5 and 6

What children should know how to do by the end of Year 4

Clear the display before starting a calculation

Children are less likely to make errors if they clear the display as a matter of habit before starting a new calculation.

Correct mistaken entries by using the clear entry key

Children tend to trust the calculator, which 'never goes wrong', without thinking about the possibility that they have made the mistake when entering numbers. Most children will clear the display and repeat the calculation if they think that they have made an error. They need to learn how and when to use the [CE] key.

Carry out one- and two-step calculations that involve all four operations

Most children have little difficulty with entering a one-step calculation to work out, for example, £4.55 [×] 17. However, when they are solving word problems, children are not always clear which values and what operations to use. They may misinterpret the question and enter the wrong calculation using the wrong values. It is good practice to get them to write down the calculations involved so they can check they have used the right operations and numbers.

Interpret the display correctly, particularly in the context of money

Children need to be taught how to interpret the displayed numbers, particularly large numbers as there no gaps to help them read it correctly. Decimal numbers can cause confusion when there is only one decimal place and the value has to be put into a context such as money.

Recognise negative numbers and use the sign-change key

Children may miss the minus sign that indicates a negative number. This usually appears on the extreme left of the display. It will appear if a subtraction calculation has been entered in the wrong order, for example.

What children should know how to do by the end of Year 5

Estimate the likely size of the answer and check answers appropriately

This is an important skill - errors in making entries often lead to answers that are nonsense, particularly when decimals or fractions are involved. Using some checking strategies, such as rounding and making an estimate or carrying out the inverse operation, will help children to avoid such errors.

Carry out measurement calculations and interpret the answer

Entering decimal numbers to carry out calculations that involve measurements can cause difficulty. It is not always clear if the decimal point has been entered until other entries are made and the numbers start moving along the display. For example, 5.6 could mean 5 metres and 60 centimetres, or 5 kilograms and 600 grams, and so on. In addition, children need to be taught to change all measurements to the same units before they do a calculation. This is best done manually before the values are entered.

Solve problems involving fractions

To find of 260 g children need to be taught that this calculation is represented by the calculation 260 [×] 3 [÷] 4, or recognise that the decimal equivalent of is 0.75 and use the calculation 0.75 [×] 260. These approaches support children's understanding of how a fraction is used as an operator and the equivalent representations of number as a fractions or a decimal. The use of fraction keys that are available in some calculators is likely to cause confusion and should be avoided.

What children should know how to do by the end of Year 6

Solve problems involving multi-step calculations

Children need to be familiar with the order of operations so that they choose the correct sequence in calculations that involve more than one step. They also need to practise jotting down parts of a calculation as they go along. Calculations such as: 8 × (37 + 58), 43 per cent of £285, or of 980 km are all multi-step and need to be taught and practised. At Key Stage 2 there should be no particular need to use a calculator to work out percentages, but if necessary the percentage can be represented as a fraction or decimal. So 43 per cent of £285 can be calculated as 285 [×] 0.43, or as 285 [×] 43 [÷] 100. Basic calculators usually have a memory. While there is no requirement for children to use the memory at Key Stage 2, children in Year 6 will probably enjoy learning to use it.

Recognise rounding errors

Although rounding errors are rare on modern calculators, they can still occur. Children need to know when answers are likely to have been rounded. For example, using the calculator to explore decimal representations of fractions will show that is represented by 0.1111111, but when this number is multiplied by 3 and 3 again the answer displayed may be 0.9999999, not 1.

Recognise recurring decimals

Children should be familiar with decimals representations such as and 0.3333333. They also need to recognise that not all the digits may recur in a decimal representation of a fraction, as in , with the decimal equivalent 0.1666666, or , which is 0.1428571 with the six digits 142857 recurring.

Use brackets, the memory and square root key

Children who have a good understanding of number and who are confident with the calculation aspects identified above may explore a range of extra facilities offered by the calculator. The memory is useful when undertaking multi-step calculations or generating more complex sequences, brackets help demonstrate and cope with the order of operations and the square root key opens the door to exploring a new set of non-recurring numbers. These skills might be developed after the end-of-year tests to support extended work and investigative activity or might be introduced earlier to children who are on course to attaining level 5.