I was rather shocked to find that my new S1 class are really lovely but had never heard of the term average. Maybe I ought to have used the term mean, but I don’t think that would make much difference. So out came the calculators and I explained that mean average was all the numbers shared out evenly.

The mean is the average of the numbers.

It is easy to calculate:

**add** up all the numbers, then **divide** by how many numbers there are.

I asked student to use calculators to find the mean average of:

600, 100, 900, 450, 50

The mean average should be 420, the mean must be bigger than the smallest number and smaller than the largest number.

Some students got 2060. These are the ones that didn’t push the equals button between adding them up and dividing by 5 (as there are 5 numbers). So the calculator did the sum

600+100+900+450+ (50÷5)=600+100+900+450+ 10=2060

So using your calculator either do

600+100+900+450+ 50= ans÷5 =420

or

(600+100+900+450+ 50)÷5=420

Now this is OK with nice round numbers but we were using time, so students needed to fix their calculators to prevent calculator diarrhoea! (this is a Mrs Physics term and not a recognised scientific term)

We can FIX calculator diarrhoea (the tendency to write down everything that comes up on the display) using the FIX button on your calculator.

Here goes (I’m using my Casio fx85 or fx83)

Step one: Press the SHIFT and then MODE button on this line under the screen. This will bring up the menu.

Step 2: Make sure that the calculator is in line mode, so press 2

Step 3: Repeat step one but this time press the 6 on your calculator which brings up the FIX button. It will then ask you to record how many decimal places you need. This will depend on your values and measurements, but a suggest 2 is a safe bet.

Step 4: Select the number of decimal places you want to use.

Step 5: You’re ready to go.

Step 6: If you want to return to normal. Press the SHIFT followed by the MODE button and then 8 for return to normal. You will have 2 options, 1 (maths mode, good if you want fractions), 2 (line mode, good if you don’t want the fractions)

Try it and let me know how you get on!

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