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?)

lougle Sun 10-Nov-13 23:28:59

www.aaamath.com/g2_32_x1.htm

50 rounds UP to 100; 49 rounds DOWN

usernameunknown Sun 10-Nov-13 23:29:37

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

usernameunknown Sun 10-Nov-13 23:30:58

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 grin

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

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

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.

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

I made it 2650
2749

Aswell. confused

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

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.

lougle 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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