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(40 Posts)
Joelsnan Tue 18-Sep-18 09:36:46

I occassionally do those games that appear on Facebook, usually the ones where you have to calculate the answer.
I always use mental arithmetic, the way I was taught at school and am reasonably confident in my answer (after check and re check).
My posts often concur with an average number of other posters however there are some whose response is quite different and alongside their response they usually put 'use BODMAS'.
I have seen this word before, where has it come from? I have no idea what it is and why it gives a different answer. Which one is considered right. Is everyone else now using BODMAS in their calculations?

Marydoll Tue 18-Sep-18 09:41:29

Joelsnan. BODMAS is taught in maths lessons schools. It is a set of rules, used when doing multiple calculations.

This may explain it.

Joelsnan Tue 18-Sep-18 10:03:40

Thanks Marydoll
I will check this out.
Why though does it give a markedly different answer to the method of calculation I and obviously many others were taught. Which is the right answer?

Auntieflo Tue 18-Sep-18 10:13:32

Is it me, or have these new rules made it more complicated?

oldgoat Tue 18-Sep-18 10:26:03

We used BODMAS at school in the dark ages (1960s ). It's not new.

Elegran Tue 18-Sep-18 10:32:26

For instance, with the sum 5 + 3 x 4 you could start by adding the 5 +3 (and get 8) then multiply that by for, ending up with 32.

If you follow the BODMAS rule, which I remember from my schooldays so it is not a "newfangled" thing, you would do the parts in the order Brackets, Of, Divide, Multiply, Add Subtract. You would start by multiplying 3 x 4 (and get 12) then add the 5 to that 12 and end up with 17.

I think the order was settled on just because of these possible differences.

Elegran Tue 18-Sep-18 10:33:05

My dark ages were the 50s. We used BODMAS then too.

Elegran Tue 18-Sep-18 10:36:12

Starting by sorting out the brackets is obvious, because that is a mini-sum of its own. If you wanted to get the first answer I reached, you would put the (5 + 3) into brackets.

kittylester Tue 18-Sep-18 10:36:37

I use BODMAS too.

Auntieflo Tue 18-Sep-18 10:48:08

Apologies to all. I left school in 1957, and I didn't get my GCE '0' level maths. sad so I evidently wasn't concentrating

ginny Tue 18-Sep-18 10:58:19

I was at school in the 60’s and have never heard of it.

Elegran Tue 18-Sep-18 10:59:41

Sounds as though you are of my vintage, Auntieflo. I think we were told the BODMAS thing in primary school, when we first started doing multi-part sums, but it was a long time ago. Maybe it was when we were in secondary and starting on algebra, where the sums get even more complicated and the rules are more essential.

Blinko Tue 18-Sep-18 11:02:44

I didn't come across BODMAS at the various schools I attended in my travels as an army child. It could have been one of those 'rules' that fell between two schools so I missed it.

I can't say I've missed it.....

Jalima1108 Tue 18-Sep-18 11:03:58

I doesn't make much sense without any brackets anyway - the answer could vary as Joelsnan has demonstrated.

We used the BODMAS method too, but without knowing what it was called.
Some algebraic equations we used to do would cover more than one page, so brackets were essential part.

Elegran Tue 18-Sep-18 11:08:20

Thinking about it more, writing a sum as 5 + (3 x 4) = ? is the beginning of using algebra - a way of logically setting out the sum for a problem which in words would be "I have five single oranges and three packs of four apples each. How many pieces of fruit do I have?" It gives the right (common sense) answer, which you wouldn't get by leaving out the brackets and working it out from left to right in the order it is written.

Elegran Tue 18-Sep-18 11:11:14

All those problems we had to solve which left our brains scrambled - they were an attempt to have us thinking logically and deciding just what we had to do to all those numbers to work out the answer.

kittylester Tue 18-Sep-18 11:31:25

I didn't know it was called BODMAS either but do remember the mantra Brackets Off, Divide, Multiply, Add, Substract.

I loved maths at school and I come in handy for some maths home work. The thing I hated was Logarithms - what are they for? confused

humptydumpty Tue 18-Sep-18 11:45:09

ginny I was also at school during the 60s, I don't know how you never heard of BODMAS.

If the sum presented by elegran, 5 + 3 x 4, was presented as to a computer as written, the answer would be computed as 32 because it would be calculated from left to right, hence when coding the brackets have to be inserted (or the order changed) to get the right answer.

kathsue Tue 18-Sep-18 11:51:06

I used BODMAS at school in the 60s. Nowadays they use BIDMAS according to DGS. The I stands for indices.

I remember Logarithms too. They were a way of working with very large numbers before the days of calculators.

humptydumpty Tue 18-Sep-18 11:54:27

And I remember slide rules!

JackyB Tue 18-Sep-18 11:57:36

I've never heard of it and got to A level maths without it.

Elegran Tue 18-Sep-18 12:08:37

But did you do it, even without the acronym? Did you work out what was in brackets before applying an operation to the contents of that bracket? For 6 x (5 + 3) would you make the answer 33 or 48?

Did you divide or multiply before adding or subtracting?

If you did either of these things, then you used the rule, even if you didn't know the acronym for remembering it.

SueSocks Tue 18-Sep-18 12:24:58

As an ex head of maths I would like to just back up the people who say it isn't new! I learnt it in the 70s and we still teach it today, although we tend to call it BIDMAS today, ie BRACKETS, INDICES, DIVISION, MULTIPLICATION, ADDITION AND SUBTRACTION.
Elegran explained it really well. We can't get 2 different answers to a sum like 5+3x4, which is why the rules of BIDMAS apply. Someone mentioned computers, well if you were to type this exact sum into a scientific calculator you would get 17, the correct answer, because the calculator has been built to recognise BIDMAS so it does the multiplying first to get 12 then adds the 5 to get 17. Many cheaper non-scientific calculators are not built to do this - creates a problem as you get the wrong answer!
At school I never understood what "Of" in Bodmas meant and it was never fully explained. Most people today use the word BIDMAS with the I meaning Indices which is basically squaring, cubing etc so you work out any brackets first, then do any indices after this you do your multiplying and dividing and finally any adding or subtracting.

Joelsnan Tue 18-Sep-18 13:31:17

I was taught to do whatever was in the brackets first i.e.
50 x 3 / (6 + 4)
I would get 10 from the brackets then 150 from outside the bracket.
I would then divide 150 by 10 = 15
How would this be done using BODMAS ?

Elegran Tue 18-Sep-18 13:39:24

50 x 3 / (6 + 4) would be

= 50 x 3/10 (B for brackets first)
= 50 x 0.3 (D for division next)
= 1.5 ( Multiplying 50 by 0.3 gives you 1.5, not 150.)