maths problem

[rsvp]

have just seen this and would welcome thoughts from greater brains than mine!
4x4+4x4+4-4x4 = ?.......I got20 but has been a long time since I was at school.
My reasoning is .....
(4x4)+(4x4) = 32
32+4= 36
- (4x4) 16 therefore answer is 36-16 =20

Very happy to be proven wrong but would love to know why!!! thank you

[factor-fiction]

^"I just don't geddit"
It's just a rule/convention, Boo, that we need to remember to follow.

Personally, I prefer to insert brackets. And I'm never sure how to apply Bidmas/Bodmas if you have something like 4÷2x4÷2

Even people like Carol/Rachel on Countdown don't set calculations out properly..

[Mojo-Jo-Jo]

I got 20.
Bodmas is:
Brackets
Orders, so anything by a factor of, e.g. squared or cubed
Division and multiplication. Both are equal
Addition and subtraction. Again, both are equal so for this problem you do the multiplication first because it ranks above the addition.
Once you have the answers to all the multiplications in place, you work on the additions and subtractions from left to right, as they are all equal to each other.

[B00]

Because I don' understand why you need brackets Mark. To put this sum in its simplest form...

If I had 4 cakes, and timsed it by another 4 and added another 4 and so on, i'd end up with 320 cakes.

[mike11111]

A "complex mathematical operation", eh?

OK, fairly easy for an Englishman but a bit taxing for a Jock! (... gets his coat and leaves).

[Mojo-Jo-Jo]

Something like that is done left to right Factor as there is no one operation outranking the other.

[mike11111]

No, Boo because you would have eaten half of them long before you got to the last tin.

[B00]

lol, probably.

[MarkRae]

> 4÷2x4÷2

Again, what's the problem? Division before multiplication, so (4/2) = 2, so 2x2=4

[factor-fiction]

It's just a rule/convention, Boo, that we need to remember to follow. Without a rule different people will come up with different answers to a calculation like this

[sunny-dave]

There are conventional rules of arithmetic precedence - you apply them - you get 20 .... simplez

[Mojo-Jo-Jo]

You will get the same answer going left to right Mark.

4÷2=2
2x4=8
8÷2=4

[ummmm]

I actually get it :-)

[Prudie]

Thank heavens ummmm ;-)

[B00]

no they wouldn't factor- you do that sum without brackets and you get 320.

Think i should give up, as I know you're all right, and im wrong, I just can't wrap my head round why.

[factor-fiction]

Okay what about 4÷2÷2, Mark.
I'm sure you'll say it's 1 but I can see why some might say 4

[rsvp]

Boo that's exactly what I did originally - 4 cakes times 4 cakes etc etc but then I remembered that you have to apply the Bodmas theory to these sorts of problems or everyone ends up doing things differently and the whole world stops. Probably not logical or particularly brilliant but that's just the way it is. x

[cathfromsaron]

i say 'of' not 'order' because i am old x

[MarkRae]

> You will get the same answer going left to right Mark.

That is a totally irrelevant coincidence.

[Mick-Talbot]

I never thought a maths thread could be so gripping.

[factor-fiction]

It's just a rule, Boo. If you follow it you get the right answer. If you don't you get 320 or some other wrong answer