Whats 12.949 rounded to one decimal place

[Clarissaintheway]

........?

What is BODMAS?

It stands for brackets, orders, division, multiplication, addition, subtraction.

It’s a way of remembering the orders of operation, which is basically which order to do the parts of a calculation in.

One serious issue with calculators and computers for that matter is something called 'rounding errors':

Consider this:
1.44 +
1.44 +
1.12

and I want the answer to 1 decimal place.

One person could add the three together using both decimal places, THEN do the rounding... they will get 4.0

However, if someone rounds the numbers first (1.4 + 1.4 + 1.1) they will get a figure of 3.9

This has actually caused serious issues in very complex math problems... like keeping a satellite in the right position, or launching a rocket, as rounding errors build up and build up to a point where a lot of inaccuracy starts to happen, a bit like if your car mileage was only 2 meters out in a 1km journey, but over 800km you could be 1.6km from where you think you are. Imagine that on a trip to the moon!

You can disagree all you like ‍🤷🏻‍♀️ it doesn’t make you right.

Right back at you.

But people will ‘argue’ if they still believe they are correct and other posters aren’t. It’s human nature ‍🤷🏻‍♀️. Point them to the explanation and ask them why they think they’re correct. HELP them, don’t belittle them.

Oh god, is rounding the new BOMDAS?



Although I think you’ll find it’s BIDMAS.

Actually, you may find it's PEMDAS 

B rackets
I ndices (powers of)
D ivision
M ultiplication
A ddition
S ubtraction

it used to be BODMAS ( O = Order = Power )

Remember the phrase 'an order of magnitude' - that where it's from.

Different countries use different terms. Some say Brackets, some say Parentheses etc. but the principle remains the same.

(1 + 1) * 2 + 1

Brackets first -

(2) * 2 + 1

then Multiplication -

4 + 1

Then the addition -

5

Hope that helps to explain the order to process it.

Tornfromtheinside, this is why I left science! I now work in the arts and it's much less stressful.

Science is an art!

OP... drags the thread kicking and screaming back on course

OP?? If you are still reading, perhaps you might like to bring this issue to the attention of your dc's teacher, and let them know that their method of marking seems to have a built-in failure mechanism.

That is true! I used to play with chemicals now I play with hot metal! So, different kind of art then!

My favourite thing from this thread is the image of a rocket popping out into space and the rest of the world going "eh, guys... the moon is around the other side".

Talking about different countries I remember when an English billion was different to an American billion and now they’re the same as we adopted the American way.

I frequently have to try and explain to people why sometimes if you round then add you get a different figure to if you add then round, therefore they need to set out at what stage rounding should occur.

In my case it’s if rounding should occur. Somehow 0.7 seems to have become an acceptable decimal equivalent for 2/3. Which frequently throws calculations out.

My favourite thing from this thread is the image of a rocket popping out into space and the rest of the world going "eh, guys... the moon is around the other side".

haha but Mumsnet promised it would be here!

I’m agog that so many people think the answer is 13.

Place it on a number line and see if it’s closer to 13 or 12.9.

Brackets vs parentheses isn't a major problem.

Now decimal points vs decimal commas...

12.949 is less than 12.95 so rounded to 1 dp is 12.9

The earlier rounding occurs, the less accurate the result.

Basically, you need to keep as much accuracy as possible until the end, then you can ditch the insignificant stuff.

Best way to explain this one is... if you give someone directions, it's best to be very accurate right up until they get closer to the final destination, then any inaccuracies at the end will still leave them close to the place.
But if you give a single wrong turn at the start of the journey, they could end up literally nowhere near the right place.

Those pesky orbital mechanics!

When my kids start learning to round, I will need to remain much calmer when they make mistakes.

Sorry for derailing OP. Hope the teacher can reassure your son tomorrow.

I mean, what place value does the 2 have in this number? Depends where you are in the world.

231,864

en.wikipedia.org/wiki/Decimal_separator

12.9 and x=3

I'm surprised at people that can't round numbers and they have said they've never had to do so in real life.

A simple way to round numbers is;

Decide how many decimal points you want to keep.
Look at the number to the right of that number, if it's less than 5 then leave the number the same (rounding down) if it's more than 5 then increase it by 1 (rounding up).

12.949

Rounded to a whole number is 13
Rounded to 1 decimal point is 12.9
Rounded to 2 decimal points is 12.95

Ilovechristmaslights: 'It is important to create an environment where nobody is scared to post'

But surely if your maths is so poor that you cannot get the correct answer (but are trying your best), then why respond to a maths question.

@starzig they clearly don't realise their maths is bad. They think their answer is correct.

Those of you with the pecualiar idea that you go all the way to the right and then work your way back, can one of you please round pi to one decimal place for me? I’ll wait..