Using the answer button in calculations
This week I want to talk about how many students find an answer on a calculator and then immediately press clear, some before they have even written down the answer. I'm not sure why this is, but I see it too often. Pupils then take time retyping numbers into the calculator, sometimes transposing some of them.
Using the calculator then becomes even harder when they are dealing with decimal answers and errors occur when they choose to round these part way through the calculation.
There are many aspects here that we as the teacher need to explicitly teach from as early as possible.
Working with numbers that are not integer values
Most calculators today will display non integer answers as either a mixed number or an improper fraction. It is important to discuss with students that this is the most accurate form of the answer, yes it is true that there are many terminating decimals that we can use but there are many more values that are not. Fractions represent the whole number whereas a decimal value (especially if the pupil rounds or truncates it) may not.
Calculators can also display answers in surd form or in terms of pi. Pupils should have as many opportunities to work with these values as possible too.
To build on this we could use the calculator to explore what happens when we add values of pi or surds to show that they follow the same rules.
If pupils can see how these values still work in this generalisation they may feel more comfortable working with numbers they see as 'different and have less of a desire to work in decimals and only change to a decimal once the full calculation is completed. See my last blog to see how to convert an answer to a different format.
Using the last answer
The newer calculators now have a function where you can use the last answer in your next calculation. It is important to teach our students how to use this button.
There are two different techniques when using the answer button that we as teachers use all the time but I know I am guilty of not explicitly teaching these to my pupils and therefore rarely saw this function used.
I think about those GCSE exam questions where an answer from part a is used in part b and how many times the number has been typed into the calculator incorrectly in part b so marks are lost even though the student knows the correct method. Having a secure knowledge of how to use the ANS button could help to resolve these issues.
It will also help when doing calculations in later years such as compound interest and iteration.
It may also stop me wanting to shout "Don't clear your screen" every time I see them instantly get rid of their answer.