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GCD and LCM
Last time my blog looked at the format button and how this changes depending on what you are doing.
Today I want to start to look at a different menu, the catalog button.
Unlike the format button the catalog button does not appear to change.
The first option is Func Analysis. If you have been looking for the log functions this is where they have gone.
The second option is probability.
This is where the percentage button along with the factorial, permutation and combination buttons have moved to.
However it is the third option I want to delve into today. When you press this option the top two choices you have are GCD and LCM.
LCM we all recognise as Lowest Common Multiple but what is GCD? GCD stands for Greatest Common Divisor or in other words Highest Common Factor. See the how to cards below on how to use each one.
Once again I am not saying this is all you teach the pupils but just as I mentioned in my blog about marking their own work there is no reason why students could not be shown how to do this in the same lesson as they are taught the skill in the first place.
Yes of course this relies on all the pupils having the new calculator as this feature is the first I have talked about that is not on the old version of the calculator, and nor is it on the 991 CW.
But how else could this be used?
The cards below show the instructions for calculating HCF and LCM with prime factors.
Think about how you could introduce the topic here using this. Pupils could be given some numbers which have already been decomposed and pupils can find the HCF or LCM. Can they work out what is happening each time? We as the teacher could then show them from the prime factor lists or using a Venn diagram where these numbers have come from. Sometimes discovering for themselves can be better than just trusting the teacher that what they are saying is true, plus you are getting the pupils to practise three calculator skills at the same time, writing numbers using powers, using HCF or LCM and using the format button to change the answer they get into prime factors.
The decision to not have this function on the 991 CW has caused its own problems in schools. Which calculator would you advise your students to buy and does it depend on the tier they are sitting?
If you have an answer to this please get in touch as it is a discussion being had in some of the departments I visit.
If you want all of my calculator how to cards they can be found at the following links. The fx-83GT CW cards will continue to be updated as I find out more.
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