Whats 12.949 rounded to one decimal place

[Clarissaintheway]

........?

12.9

teacher and 11+ tutor here. Please ignore all these people rounding all along the line.

🤦🏼‍♀️

I now get why lawyers get so cross when non lawyers start claiming to know the law!

12.949 rounded to 1 d.p. is 12.9. As is 12.9499,12.94999 and 12.949999999999999999999999999.

Because they are all less than 12.95.

12.95 is the smallest number that is rounded up to 13.0 when rounded up by 1 d.p.

You don’t round up starting from the right because that is destroying (relevant) information. The number is 12.949. You are rounding it - not some other also rounded number. The whole point of rounding is that it is an approximation.

Otherwise it is like me trying to get my 8 year old on a sports course for age 10+. “She’s nearly 8 and a half, which is nearly 9 which is practically 10.” “So she’s just 8 then.” “Well - yes - technically.”

(Cambridge maths degree)

But Teentimestwo it's NOT 13!!!

PurpleDaisies, I was agreeing with you.

Yep, this thread is also making me want to throw things.

12.949 is closer to 12.9 than 13.0.
So if we want to round to the nearer 0.1 we must choose 12.9.

RandomWok
You are getting 13 because you are rounding 12.95 (a completely different number) to 1 decimal place, not 12.949.

12.949 rounded to one decimal place is 12.9 (you look at the next digit along ie the 4 which rounds down)

Come back "toe/tow the line," all is forgiven!

Though interestingly, had the question been to round 12.959 to 1dp, I would personally give it as 13.0 to make clear the level of accuracy I had rounded to. I don't know what the 'official' rule is on this though.

That is correct.

13.0 is a very different number to 13.

13.0 means between 12.95 and 13.05. 13 means between 12.5 and 13.5.

OhDear I know that! I was discussing what answer you would write if you rounded 12.959 to 1dp.

(Cambridge maths degree too)

www.bbc.com/bitesize/guides/zv3rd2p/revision/3

To round a number to a given number of decimal places, look at the number in the next decimal place:
If it's less than 5 , round down
If it's 5 or more, round up

www.bbc.com/bitesize/guides/zscq6yc/revision/2

Rounding to decimal places
When rounding using decimal places (dp), the degree of accuracy that is required is usually given. However, there are certain calculations where the degree of accuracy may be more obvious. For example, calculations involving money should be given to two decimal places to represent the pence.

To round to a decimal place:

1. look at the first digit after the decimal point if rounding to one decimal place or the second digit for two decimal places
2. draw a vertical line to the right of the place value digit that is required
3. look at the next digit
4. if it's 5 or more, increase the previous digit by one
5. if it's 4 or less, keep the previous digit the same
6. remove any numbers to the right of the line

Examples

Round 248.561 to 1 decimal place, then 2 decimal places.

248.5|61 to 1 decimal place is 248.6
248.56|1 to 2 decimal places is 248.56

Notice that your answer should have the same number of decimal places as the approximation asked for.

Round 0.08513 to 1 and 2 decimal places.

0.0|8513 to 1 decimal place is 0.1
0.08|513 to 2 decimal places is 0.09

12.959 is rounded to 12.96. Which is rounded to 13.

justaguy

Those of you saying 13 - for the love of God, please don't help any children with Maths homework until you've Googled the rules for rounding.

Thank you Mum I thought it was, but I get rusty on the niceties sometimes.

12.9. Anything else is a double rounding error.

@quizqueen

No.

2.49 would round to 2.5 not down to 2.0 if you're doing to 1 decimal place.

I'd you're doing whole numbers then 2.49 would become 2 and 2.5 would become 3.

TeenTimesTwo, Sorry. Have re-read your post now. Head exploding.

12.949

12.9 are considered the significant digits (to 1 decimal place)
0.049 are the insignificant digits. Anything less than half of the last significant digit (49 in this case) is rounded down, and anything else rounded up. So in this case round down.

Had the number been 12.950 then the result would be 13.0

We ALWAYS count the significant digits first, then work on the insignificant ones, not the other way around.

@TeenTimesTwo

Cricket mum is talking nonsense.

If you're rounding to 1 decimal place then 12.959 does not become 12.96. The 9 at the end doesn't come into play at all. You ignore it.

12.959 to 1 decimal place = you only look at the number directly to the right of the decimal you want. You want the first decimal, so you look to the second, which is a 5. That means you round the 9 up to 13. In that example, you get the same answer but you won't always and cricket was wrong.

Only look at the digit directly next to the decimal you want.

If the number was 12.95986254892282846382837392984729654413343673893

Would you go all the way to the last 3 and round every single number if I said "round to 1 decimal point"? No. You wouldn't. You would only look at 2 number; the decimal point you are rounding too and the nunb3r directly to it's right.

Teentimestwo Always good to wave at a fellow Tab Mathmo!

I'm guessing from our two user names that you wer a bit earlier than me. (I was late 90s, early 00s.)

What do you mean? The answer is 12.9, not 13. I haven't rounded it incorrectly at all. I was trying to explain what 1 decimal place means - possibly badly.
Sorry, it wasn’t clear that you were doing that. I thought you were answering the op and explaining why 13 rather than 13.0 was the right answer.

13
12.959 is rounded to 12.96. Which is rounded to 13.

Rubbish.

The first one is defo 12.9

Second is 3 but my method is so weird I'm not going to type it out!

4/5 of 60 = 4 divided by 5 x 60= 48 (this is probably not the way they teach it, but it's the way that makes sense to me! You can also do 60 / 5 x 40 which also gives 48, so the answer is definitely 48!)

Tell your son well done! I'm 32 and struggled with those questions a little haha.

Bet you're really glad you started this thread OP