# Mumsnet Talk

## Maths question!

(47 Posts)
RosinaCopper Sun 10-Nov-13 22:37:46

Ds was set the following question:

2700 people attended a local event. To the nearest 100:

What is the smallest number that could've attended?
What is the largest number that could've attended?

Ds was a bit stuck, so me, DH and he discussed it before completing it and handing it in. According to his teacher we are wrong! So, I'm interested to know what you think the answers are, (and if you agree with us, whether to raise it with the teacher?)

itsjustplayingonmymind Sun 10-Nov-13 22:40:22

Smallest 27
Max 30
I may be wrong

Sun 10-Nov-13 22:41:05

2650; 2749

Sun 10-Nov-13 22:42:54

The reason I give those figures is that if you round, then half our more of the rounding figure round up, less than half rounds down.

StarsAboveYou Sun 10-Nov-13 22:43:48

I'm with Lougle

starlight1234 Sun 10-Nov-13 22:43:51

agree with Lougle...

What did teacher say ..what did you say?

Surely both answers are 2700 if you know that's how many attended?

What a stupid question

CrocodileScream Sun 10-Nov-13 22:43:54

That sounds nonsensical to me.

RosinaCopper Sun 10-Nov-13 22:44:08

lougle that's what ds had as his answers! Wrong, according to his teacher.

But it doesn't say 'approximately 2700 attended'

CrocodileScream Sun 10-Nov-13 22:45:47

Ah I see what you mean Lougle but the way it is written it seems like it wanted you to present your answers to the nearest hundred. Badly written question.

Sun 10-Nov-13 22:46:00

I agree with lougle

PiqueABoo Sun 10-Nov-13 22:46:12

Definitely:
2650
2749

RosinaCopper Sun 10-Nov-13 22:50:35

The exercise was about rounding and the teacher marked 2650 as wrong and wrote 100 (we think she made a mistake there!) and marked 2749 as wrong and wrote 2700.

Given that the exercise was about rounding, it seems mad to have both the answers as 2700!

But we also thought that the question was badly worded and perhaps if it has said 'to the nearest 100, 2700 people attended' and then asked for the smallest and largest numbers, we would have been correct.

The thing is, would you raise it with the teacher (it's not long until parents' evening), or let it go this time, but keep an eye on future homework? I don't want ot be a nightmare parent who thinks her little darling is always right, even when they're wrong IYKWIM!

starlight1234 Sun 10-Nov-13 22:55:32

A friend of mine had an issue with a wrong answer in homework book..Dad wrote a comment in book and she agreed with what he had said...

Sun 10-Nov-13 22:58:19

Ah, so she's saying that just one person could have attended, but that would be 100 to the nearest 100. 2700 would be 2700 to the nearest 100.

My fault for turning a stupid question into a logical one

RosinaCopper Sun 10-Nov-13 23:05:27

I'm just glad that it's not only us that misunderstood a badly worded question!

PiqueABoo Sun 10-Nov-13 23:07:33

If they missed out "Up to.." or whatever off the front of the question then I think 1 -49 attendees to the nearest 100 is zero. So

0
2700

They probably didn't do that though, so I would explain to child that to err is human and count your blessings that they haven't yet been rated an entire SATs level (not sub-level) too low for maths, as happened to my DD.

steeking Sun 10-Nov-13 23:07:58

I agree it was worded really badly. It should have said "To the nearest 100 people, 2700 attended the event" that's the rounded number.
The miminum attendance that would round to this figure would be 2651 (if its 2650 you round to the even number so that would be rounded to 2600).
The maximum would be 2749 as you stated, 2750 would get rounded to 2800 following the even/odd rule.

steeking Sun 10-Nov-13 23:16:21

Actually if someone could clarify the odd/even thing I would be grateful as I'm starting to doubt that. It is def what Ds's were taught in the last couple of years.
I was taught what lougle said.

RosinaCopper Sun 10-Nov-13 23:21:35

I din't know there was an even/odd rule (it's a very long time since I did 'O' level maths!)
I also thought that 5 was always rounded up, and that with rounding to the nearest 100 you could ignore the units and just consider the tens - we had to explain to ds why the maximum was 2749 and not 2744 which was his first answer as he felt that 749 would be first rounded up to 750 and then up to 800 based on the 'high five' rule that he's been taught.

I'm obviously not as good at maths as I thought!

RosinaCopper Sun 10-Nov-13 23:23:26

Sorry, slow typing and laundry!

I'd like a clarification of the even/odd thing, too, as I was also taught what lougle said which is why our answers were the same!

Sun 10-Nov-13 23:25:54

You can't round twice!

Sun 10-Nov-13 23:26:45

I still don't get why you can't just argue that the answers are both 2700 because they wrote such a shitly worded question.

The teacher should have been on our last maths thread where we were discussing how often wording makes the difference to how how we answer a maths question.

Sun 10-Nov-13 23:28:59

www.aaamath.com/g2_32_x1.htm

50 rounds UP to 100; 49 rounds DOWN

I agree thewoman. The way the question has been phrased in the OP doesn't make it mad for both answers to be 2700

Or you could argue (based on the OP) that the minimum to the nearest 100 is 100 COULD have attended but the maximum number attending could be based on the capacity of the venue

RosinaCopper Sun 10-Nov-13 23:39:56

lougle I explained to ds about not rounding twice - ie ignoring the units and only considering the tens, with 49 being the highest number under 50, therefore 2749 being the highest number we could use to give 2700 as the answer to the nearest 100. But this was marked as being wrong.

Maybe I'll just mention to the teacher that in my opinion the question was badly worded. I just don't want to be a pain of a parent (at a maths workshop at the school a few years back, a different teacher had maths examples up with wrong answers on (I mouthed the correct answers rather than saying them out loud), and spelling mistakes on wall displays, so perhaps I'm fighting a losing battle?)

I despair though, because now my word isn't good enough against his teacher's word, whereas it alwasy used to be, but I suppose that's school for you!

RosinaCopper Sun 10-Nov-13 23:41:37

Thanks for your comments, I'm off to bed to try to get a bit of sleep before my alarm call from my youngest (which is usually around 5am). But that's a whole other thread!

PiqueABoo Sun 10-Nov-13 23:42:28

In the K2/KS3 curriculum they do standard rounding i.e. 5 rounds up to 10 (if rounding to the nearest 10).

Even/odd is another method.

steeking Mon 11-Nov-13 00:58:50

Maybe it was me that got taught the odd\even thing and the dcs that got taught the standard way! my brain has a habit of dragging up weird stuff from the past...

ClayDavis Mon 11-Nov-13 01:08:54

I think the odd/even thing was discussed on one of the maths threads that was running in chat for a while. Can't for the life of me remember what the conclusion was. The standard conventional method would be that 5, 50, 500 etc round up to the next 10, 100, 1000 etc.

Mummyoftheyear Mon 11-Nov-13 06:46:44

Smallest: 2700
Largest: 2749

Silly question set by teacher.

Mummyoftheyear Mon 11-Nov-13 06:47:34

Oops
Smallest: 2650
Largest: 2749

Mon 11-Nov-13 07:07:33

if its to the nearest hundred then the answer must end with '00' so I would have probably have put 100 and 2700.

Mon 11-Nov-13 07:30:00

although strictly speaking if there were less than 50 going then the nearest 100 would be 0.

answers that end with 50, 45, 41, etc are not to the nearest 100 as you have given 10's and units too.

Mon 11-Nov-13 08:13:02

I'd have said 100 and 2,700 too, but I think I'm looking at it from a logic point of view, rather than a mathematical one.

richmal Mon 11-Nov-13 08:22:05

I agree with Jayne

Assuming 2700 were an approximation, looking at the upper and lower bounds of measurement there were between 2650 and 2749 people there.

Looking at the tens digit and using the rounding rule: if it is 5 or above round up, if it is below 5 round down, both numbers round to 2700 for the nearest 100.

(There is no round to an even number rule)

Gileswithachainsaw Mon 11-Nov-13 08:36:00

2749

Aswell.

If it's about rounding why would there be no rounding involved?

Mon 11-Nov-13 09:09:48

2650 isnt to the nearest 100 though as it has a '50' at the end - the nearest 100 to 2650 would be 2700 (rounding up). 2749 has '49' at the end so isnt to the nearest 100 either. the nearest 100 to 2749 would be 2700 (round down).

If you are doing to the nearest hundred than the answer must end with '00'.

I took it as the minimum amount of people that could go is 1 and the nearest 100 to that (in the absence of rounding down to zero) would be 100

The maximum that could go would be 2700 which already has '00' at the end so that is the answer.

You cant have an answer with 49, 51, etc at the end as that isnt an answer to the nearest 100 as you have 10's and units in the answer.

LittleMissGreen Mon 11-Nov-13 09:33:34

That is a completely nonsensical question.
Because the number of people who actually attended is completely irrelevant to the answer.
The smallest number of people who could have attended (rounded to the nearest 100) is 0
The largest number of people who could have attended would be determined by how many could fit into the venue, information about which is not provided.

As to evens/odds rounding this is the 'bankers method' of rounding, but I'm sure that isn't taught in primary school.

Mon 11-Nov-13 20:00:22

It's the syntax that's the issue. I read the question, decided it didn't make sense and inserted an assumption:

Original question:
2700 people attended a local event. To the nearest 100:

In this case 2700 is an absolute. 2700 people attended, full stop.

Modified question:

2700 people attended a local event (to the nearest 100):

In this case, the 2700 is already the rounded answer, so the answers many of us gave are correct.

Mummyoftheyear Mon 11-Nov-13 21:16:32

Lougle is absolutely right.

ClayDavis Mon 11-Nov-13 21:18:22

I agree, lougle. The answer to the questions as stated can only be 2700 because it's already told you exactly how many people attended. It's complete nonsense.

Usually these are upper and lower bound questions so people have made the assumption that the question should have been that the number of people who attended had been rounded and you need to find out what the minimum and maximum number of people that could have attended was.

I'd go with username's answers of 0 and depends on the capacity of the venue. But then I'm pedantic about badly worded maths questions.

RosinaCopper Mon 11-Nov-13 22:15:51

Right, I'll mention to DS's teacher that I think it was a badly worded question, as we also made the assumption that the rounding had already been done and therefore the questions were asking about what figures could have been rounded to give that number.

Given the format of the question, I don't agree with the teacher's answer of 100 for the smallest number that could have attended, because we have already been told that 2700 people attended!

But I also don't agree with those who say that the smallest number that could have attended is 0, because they haven't attended.

What makes it slightly worse, in my opinion, is that this exercise was in a printed book. I might have to get all 'Outraged of Nottingham' and write to the publisher about it!

LittleMissGreen Mon 11-Nov-13 22:24:53

But I also don't agree with those who say that the smallest number that could have attended is 0, because they haven't attended.
Except that if 1 person attended, that rounded to the nearest 100 is 0.

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