## Saturday, 22 February 2014

### What's Your Favourite Button on a Calculator?

On Monday, when we return to school after a relaxing half-term, I will be starting a mentoring 'role' with one of the ITTs my school are taking on for the next 10 weeks. Now, this was something I wanted to do at the start of this year, but as I do not yet have the required amount of experience for the ITT provider in our area it is something I had resigned to next school year when I am capable of undergoing the training officially. However, the week before half-term we received a phone call to say that we would be getting 2 ITTs after half-term and not just one as we had previously thought. So, I have been asked to support our department's ITT mentor with the mentoring role to our 2 ITTs. He will be the official mentor to our 2 ITTs, but I will be supporting him by holding meetings, observing lessons, and just being there for advice etc. So, in effect, I am an 'additional mentor', if you like, in an unofficial capacity.

Over the past week I have been getting my classes ready for when the ITTs take them over and so have been getting their class folders all up-to-date, marking their books, sorting out the schemes of work etc so they've got as much information as they could need when teaching the classes. As I have been doing this I got thinking about my own mentor on my GTP and how we held our meetings, how the observations went, what he said to me in feedback sessions and in general what and how he taught me.
Of the MANY, MANY things I was taught that year, my mentor once asked me what my favourite button on the calculator was. Now, this was something I had never thought of before and so I was intrigued as to what his was. My mentor's favourite button on the calculator is this little beauty...

The sexagesimal to decimal button!

As such it has since become my favourite too. The button, for those of you who don't know what it is/how it works, allows you to convert between sexagesimal and decimal values. So, when working with time calculations, or with degrees, you can use the button to convert a decimal to hours, minutes and seconds.

For example, if you were working out the time it took to run 12 miles at 8mph you would get an answer of 1.5 (hours). Then, by pressing the sexagesimal to decimal button, you get an answer of 1hr and 30 minutes. This answer is separated by the open circle, apostrophe and speech marks where 0 is given for the number of seconds.
You can also convert the other way. So if you wanted to know what 1 hour and 48 minutes was as a decimal you would type in 1, press the button above, 4, 8, the button above and then equals to get this displayed in sexagesimal form, then just press the button again to display it as a decimal (1.8 hours).

Prior to writing this post I looked up the online manual for my Casio calculator (others are, of course, available) and have since found lots of other things that can be done with the button, including adding and subtracting times:

For example, if you press...
1, button, 5, 2, button, +, 1, button, 2, 5, button, = ( 1 hour 52 mins + 1 hour 25 mins)
you will get an answer of...
3, open circle, 17, apostrophe, 0, speech mark (3 hours, 17 minutes, 0 seconds)!

There are lots more examples in the manual/appendix below!

These files can be found here...
http://support.casio.com/pdf/004/fx-82ES_etc_E.pdf
and
http://support.casio.com/pdf/004/fx82ES_350ESetc._Appendix.pdf

There is usually a question on the GCSE papers that require students to work with some sort of time calculation. Whether it be a simple speed, distance, time calculation or a trickier question where a question is given in context that they have to work out.
When marking papers I have seen students write answers incorrectly when they do not realise that the decimal answers they get when working out time calculations do not correspond to the time in hours, minutes and seconds. A common misconception I have seen is when students write 1.25 hours as 1 hour and 25 minutes and not, as it should be, 1 hour and 15 minutes.

I know I wasn't taught how to use the sexagesimal to decimal button when I was at school and wonder what difference it would make to students if they were able to use the button correctly. Obviously, there is a need for students to know how to convert between hours, minutes and seconds etc, but if they are given the use of a calculator in an examination then that's what it is there for!

I know that my students need to become a lot more familiar with how to use their calculators, when working with trigonometry, geometry, fractions, powers, roots etc. It frustrates me so much when students can't even convert between a fractional answer and a decimal answer; I often get asked 'Sir, how do I get rid of this fraction' or 'Sir, I'm not getting what you've got on the board' (wrong setting [radians/degrees etc]).

So...I think this half-term I will set them a homework to explore one of the buttons on their calculator in greater detail. Get them to produce a poster about their chosen button with worked examples and diagrams of how they can/could use the button in their examinations.

My question to you then is this...What's your favourite button on a Calculator?!

Tweet me @mrprcollins or comment below...

#### 1 comment:

1. My favourite button is whatever I haven't used recently and have just 're-discovered'. So at the moment it's the sexagesimal button...thank you! The most useful button, which I wish my Y11 students would use more often, is the ANS button. Too much re-entering of rounded answers in the middle of calculations. Maybe I need to have 'calculator tip of the week'. Thanks for all your hard work and resources. Very useful out here in Bermuda...miles from any professional development!