BODMAS.. Mistake or correct?

[JellyTots2009]

My friend is at college and today learnt BODMAS. I asked her to send me an equation she had been given and her answer. I worked it out for myself and I got a different answer. Her teacher gave her a different answer too!

So this equation

3x2-4+5/2

Answers were;
-0.5
3.5 or
4.5

Which is correct and can people give their workings out please. I do think I've done it wrong but I followed the order!

4.5

3x2 = 6
5/2 = 2.5
6-4 = 2
2 + 2.5 = 4.5

I get 4.5

(3x2) - 4 + (5/2)

6 - 4 + 2.5

Because it contains both + and - I work from left to right which gets me 4.5

It’s 4.5
X and / are done first then - and + in order they come (it’s not addition before subtraction ...)

So
6-4+2.5=4.5
(Maths teacher here)

I got 4.5
6 - 4 + 2.5

3x2-4+5/2
(3x2)-4+(5/2)
(6 - 4)+2.5
2+2.5

=4.5

I got 4.5

yes 4.5

you multiply 3x2 for 6-4 =2
then you divide 5 by 2 = 2.5 then add 2 plus 2.5 = 4.5

4.5

Thanks for the answers.
See I carried on in order and added before subtraction.
Can someone tell me why that is done? Because it confuses me due to not being in order

I got 4.5

(3x2)-4+(5/2) = 6-4+2.5 = 4.5

It doesn't matter whether you do addition or subtraction first, they get the same result presuming you've done the multiplication and division already.

Do the multiplying and dividing first then work from left to right

3x2-4+5/2
(3x2) = 6
(5/2) = 2.5
6-4+2.5
= 4.5

Calypso I did the division and multiplication first. But with the answers I then carried on and added then subtracted. It's gave me -0.5. When do people know not to do it in order ?

I ront understand what your adding subtracting to get your figure

Don't *

@JellyTots2009

Thanks for the answers. See I carried on in order and added before subtraction. Can someone tell me why that is done? Because it confuses me due to not being in order

3x2-4+5/2

No brackets, no order (BO)
Division 3x2-4+(2.5)
Multiplication (6)-4+2.5
Addition 6(-2.5)
Subtraction 4.5

Really division and multiplication have equal preference.
Addition and subtraction have equal preference.

I'm guessing the mistake you made was to think it works like:

Division 3x2-4+(2.5)
Multiplication (6)-4+2.5

               6 - (4+2.5)
                 =        -0.5

That's incorrect as you are treating the - as a multiplier rather than number being -4. It's actually all addition 6 + (-4) + (2.5)

So you first do the multiplication and division which turns it into
6 - 4 + 2.5
The it doesn’t matter which order you do them as 6-4+2.5 will give the same answer as 6+2.5-4

As written I get 4.5 but if it's set out as

3x2-4+5
__
2

The answer is 3.5 as the top is 7, all divided by 2

Which as you can see is horrible to set out on a phone, so could cause confusion.

However that isn't just BODMAS but BODMAS and fractions.

BODMAS is

Brackets (none)
Order (none) (squares, square roots etc)

Division and Multiplication (3x2 and 5/2) - they are technically equal so done L to R where required.

Addition and Subtraction - also equal, so done L to R.

But if you subtracted the 4 after
6+2.5 =8.5
8-4 = 4.5

@RedskyAtnight had explained it well. You're not really subtracting 4, you're adding minus four. The + or - is attached to the number that follows it and it tells you whether it's a positive or negative number. Then you just add them all together

The + and - belongs to the number so its
+6 -4 + 2.5
Once you do the multiplying and dividing you work left to right doing adding and subtracting

You have added invisible brackets to the '' 4 + 5/2 ''

You deduct the 4 then add the 5/2.

God, maths is difficult to explain from a keyboard.