BODMAS and floating calculator

[Boxwell]

Hello,

Now I am no maths lecturer but I remember being fairly good at it in school!

I have noticed that the floating calculator when outputting to the screen forgets about BODMAS (brackets off, division, multiplication, addition,subtraction.)

For example, it will output the following:
9 + 6 * 3 = 45.

Now in my day, unless there was brackets around the 9 and the 6, the answer to 9+6*3 is 27 (told you I was good at it in school :-/)

This could be a bit misleading for students.

Interested to hear thoughts on this. maybe I am totally wrong and my maths is up the spout!!

Regards,

Graeme

[Louise Chew]

my maths has always been up the spout so I'm definately not saying you're wrong!

I have just tried this sum on the microsoft calculator & it comes out with answer 45 as well.

So it will definately be interesting to see what response we get to this.

[jepatton]

I think the problem is that the Activstudio calculator is not a scientific calculator, so it doesn't respect the order of operations. If I remember correctly, this has been pointed out before. I like the new option in Inspire to link to a different calculator on the hard drive.

[Nigel Pearce]

The Activstudio calculator is performing a running total. As you perform this calculation you will see that the answer 15 is appearing on the calculator after entering 9 + 6 *
So the next step is 15 * 3 which is 45 and therefore correct as a running total.

However, looking at the whole expression in one hit, you are right. The convention for the expression 9 + 6 * 3 is to perform 6 * 3 then add the 9.

The calculator is behaving itself, but the output for the whole calculation can be misleading from BODMAS perspective.

If you add this expression to the flipchart page, it might be an interesting exercise to ask someone to draw brackets in the correct place using the Pen Tool. ;)

[philblaylock]

I've come up against this too. I think it's a really good for discusssion: what has the calculator done wrong? And a teaching point to show that the calculator doesn't always give the correct answer (especially if it was the AP3 one!!!)

[formackiek1]

The Activstudio calculator is a BASIC calculator and these have never respected BODMAS.

Any hand-held basic calculator will also give you 45.

Pick up a scientific calculator (or switch the Microsoft calculator in Windows to scientific from the View menu) and it'll tell you the answer is 27.

As for the calculator in Activinspire, it's the same. I use a custom button on the roll-out to get my own preferred calculator.

[rrasaq]

Very interesting!! This is a good topic to let ours students know that all calculators are not built the same. therefore, they will need to know the rules before doing any computation with their caculators.
Thanks for bringing it to the limelight.