x Turn on thread page Beta
 You are Here: Home >< Maths

Which is the correct calculation? watch

1. Hi, well I am a bit confused here. I have only just heard about the order of operations.

Here's an example sum:

3-3*6+2 = -13

Does the fact that this sum = -13 if done in accordance with the order of operations have anything to do with this being an algebraic equation? And if this sum isn't an algebraic equation then the answer is 2? Or is algebra irrelevant here?

In other words in algebra it's -13 but algebra aside and in simple arithmetic the answer is 2?

The other confusing thing I also noticed today is that not all calculators follow the rule of BEDMAS automatically.

Thanks.
2. No, algebra implies the use of variables.

Also all equations follow BEDMAS, give me an example that doesnt?
3. (Original post by GUMI)
No, algebra implies the use of variables.

Also all equations follow BEDMAS, give me an example that doesnt?
When typing that sum into some calculators it kept coming back with 2. My question is in what case is each answer right? Or it doesn't matter what situation; the answer will always be -13?
4. There's no difference between using the operations on variables or on numbers. Remember, it's order of "operations", it applies regardless of what the operators are working on. In this case multiplication comes first and you get -13. If your calculator is doing something different then you should make sure to use brackets so it works in the right order.
5. It's definitely -13. Pocket calculators and other similar ones will not follow the rules of BIMDAS/BEDMAS. They're programmed differently.
Try to get a scientific calculator instead. Casio brand are the ones I would recommend.
6. So basically there are no situations where 2 would be correct? Because another way I was looking at it was that if you had 3 apples and threw them all away you would have nothing and then if you multiplied nothing by 6 you would still have nothing but then if you added two apples you would have two apples.

And of course some calculators were calculating as 3-3=0, 0*6=0 and 0+2=2. And of course other, scientific calculators were use BEDMAS.

So basically in a nutshell we must think of bid/bedmas when doing sums with multiple operators? Is this a relatively new thing or has this actually been around for decades?
7. If you wanted 2 to be the answer, you'd have to put brackets around the 3-3, since that would force you to do that part first. Since there's no brackets, -13 is the only acceptable answer. Any calculator that says 2 is wrong.

I'm not sure how long order of operations has been around but I doubt it's a new thing. I'd have thought you'd need it if you want to write algebra without it being a mess of brackets.

Posted from TSR Mobile
8. (Original post by GUMI)
No, algebra implies the use of variables
No.

(Original post by jackaco10)
So basically there are no situations where 2 would be correct?
Indeed.
9. (Original post by jackaco10)
So basically in a nutshell we must think of bid/bedmas when doing sums with multiple operators? Is this a relatively new thing or has this actually been around for decades?
It has been around for centuries.

Posted from TSR Mobile
10. I can't believe I doubted this lol. The thing was that a great many adults were coming up with the answer 2. When I tried to explain to them the order of operations dictates that the answer is -13 one or two of them told me that we must learn things differently now and that they never heard of BEDMAS/PEDMAS.

However I personally think what's really happened here is that a great many adults have forgotten about these calculations. Either that or they weren't paying much attention when they were in school.

As for the calculators that came back as 2 they are obviously calculating the sum in it's simplest form. I guess these calculators were coded without ambiguous situations being in mind at the time.
11. It's the fact that said calculators are most likely cheap and simple devices, meaning that their programming isn't sophisticated enough to follow the order of operations. Since not following the correct order has been wrong since the 17th century, any calculator that gets it wrong should be returned for a refund, and then you should buy a better model. If you intend to continue with mathematics, I recommend the TI-84 Plus CE-T, which has a number of features that are very useful at A-Level and beyond. It costs £71.95 from http://www.studentcalculators.co.uk/...lculators.html (you'll need to scroll down a bit). Alternatively, if you intend at some point to stop studying mathematics, a Casio model should be fine for elementary use.

Also regarding the point about adults - they like to criticise people who are younger than them (indeed, they did this even as far back as Ancient Greece), and to pontificate about the need for more "rigour" in the education system, but of course this is all in reality just ego. And in mathematics, it's being right that gets you the credit, not being able to shout your answer the loudest.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 24, 2016
Today on TSR

How much will your degree earn you?

Find out where yours ranks...

Poll
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants