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Primary maths help please

(107 Posts)
isitwineoclockyet Mon 10-Oct-11 09:36:03

My daughter's homework was all about odd & even numbers, & whether adding & subtracting odd & even will give you an odd or an even answer. So for example, odd + odd = even.

All very straight forward, except that some of the sums had decimals in them (31.3 + 42.6, for example)

DD couldn't do those & asked for our help. DH & I both thought the concept of odd & even only applied to whole numbers, except in certain specific cases, which neither of us can remember <old people> but which we thought were probably beyond the scope of the average primary maths lesson.

We asked our yr 9 daughter what she thought & she said she also thought odd & even only applied to whole numbers & asked whether they were supposed to round them.

I've just been & asked the school, & their answer is that if it ends in 1, 3, 5, 7 or 9 then it's odd, regardless of how many places beyond a decimal point the last digit is (so 3 is odd, 0.3 is odd, & so is 0.03.

Can anyone with a maths background confirm for me who is right?

(I should say there is some history here, including previous homework which had a 5x3 grid on it, & the statement underneath "In the 16 squares above.....")


LemonEmmaP Mon 10-Oct-11 09:39:26

It sounds wrong to me - by definition I believe that an odd number is one which has a remainder of 1 if divided by 2. Like you, I can't see how a decimal can be described as odd. I have got as far as a maths degree on that basis, so although I can't say definitively, I am with you!

catsareevil Mon 10-Oct-11 09:41:16

I agree - even numbers are divisible by 2 into a whole number. So a fraction cant be an even number.

Wikipedia agrees, if you think that is any sort of authority grin

isitwineoclockyet Mon 10-Oct-11 09:54:51


I had a brief and unproductive chat with the teacher this morning. I said that you could argue that 3.2 doesn't divide by 2, therefore it can't be even. You could also argue 3.5 is even, because you can divide it by 2 & get 1.75. He said it's nothing to do with whether you can divide by 2 or not (Really??)

I'm wondering whether by the time i've posted this someone will have come along to explain why the school is right, & 3.1 is odd, but surely if there's any difficulty about decimals & odd/even they should either have left it till later, or explained it fully to the children so they understood it (& could explain to their know-it-all parents why the school was right & they were wrong!)

DeWe Mon 10-Oct-11 10:11:12

By his argument, 3 (for example) is also even because you divide it by 2 and get 1.5 confused

Don't get his argument at all, if he'd said 3.2 is because you divide by 2 and get 1.6 which is the same order of magnitude (number of decimal places). But 3.5??????

Having done a maths degree, I would say that I would always define an even number as 2n where n is an integer (whole number). You can argue whether n has to be real or positive (eg is -2 even?) but not his argument.
(If I'm right it has to be real, but can be negative)

So mathematically speaking:
A number, N, is even if there exists a number, n, where n is in the set of Real numbers and in the set of Integer numbers, such that N = 2n
I think that's a rigorous argument. grin

isitwineoclockyet Mon 10-Oct-11 10:17:10

It's actually slightly worse than that, because he said "forget being able to divide by 2. It's nothing to do with being able to divide by 2"

I'm not sure exactly how he would define odd or even at all in that case, but as he basically evicted me at that point, I didn't get chance to ask.

I know 9am on Monday is not the ideal time to ask questions, but there are two teachers in the classroom (not TAs, two teachers), so I thought he might have managed it. Evidently one teacher was needed to take the register & the other to evict bothersome parents ;-)

GoAndDoSomeWork Mon 10-Oct-11 10:18:37

James and James The mathematics dictionary defines odd as "an integer that is not evenly divisible by 2". An integer is defined as any of the numbers ...,-4,-3,-2,-1,0,1,2,3,4... that is they are whole numbers. This teacher is about to confuse his class for life .... please try and stop him!

witchwithallthetrimmings Mon 10-Oct-11 10:24:55

shock I think you need to talk to the head about this.

The only think that might rescue him is if he was doing money at the same time
so £3.6 is an even number of pence but "its nothing to do with being divisable by 2" [shock shock shock]

Ask him what a prime number is next time you see him

isitwineoclockyet Mon 10-Oct-11 10:37:40

Sadly I can't talk to the head (seems to have something of an aversion to parents.....)

I'm torn between seeing if my husband can get any more sense out of him, & telling my daughter to go & ask him again. Perhaps she could ask him how 3.1 is divisible by 2, & if it's nothing to do with being divisible by 2, then how exactly does one define odd & even numbers?

isitwineoclockyet Mon 10-Oct-11 10:39:38

Sorry - have just realised my last post is at risk of confusing the issue even more.

I should ask him how 3.2 is divisible by 2, not 3.1. I think he believes 3.1 is an odd number!

witchwithallthetrimmings Mon 10-Oct-11 10:46:55

but 3.1=3.10 doesn't it which he would classify as an even number as 10 (and zero) are even numbers

isitwineoclockyet Mon 10-Oct-11 11:04:48


If he thinks that, then all non whole numbers automatically become even, as you could stick a zero after any of them. It wouldn't change the value, but it would change whether it ends in an odd or even number!


GoAndDoSomeWork Mon 10-Oct-11 11:05:38

I think getting your daughter to argue with the teacher who clearly doesn't have a clue will probably leave her in tears and the teacher on the defensive. Are there any other parents you can get to say something after school so it doesn't seem like you are the only one to have noticed the teachers mistake or is there a head of year/ school maths specialist you can talk to? confusing/ incorrect teaching of maths this age can put children of maths for life and your daughter will probably quite wisely zone out of maths for the rest of the school year. If he has got this wrong then he probably isn't very confident with maths and may well teach them more nonsense. What year is your dd?

If you can't communicate with head maybe you should approach governors or even the lea.

Good luck!

sparkle12mar08 Mon 10-Oct-11 11:07:44

Please go and see the head. Idiots like this shouldn't be allowed to teach, they really shouldn't. I'm serious. He is wrong, and every Nobel Mathemetics winner there ever was would argue with him too. How can he be allowed to do this? It's just wrong.

isitwineoclockyet Mon 10-Oct-11 11:25:26

Yeah - I don't really want her to have an argument with him, but if he has a correct, age-appropriate explanation for why I'm wrong to think only whole numbers can be odd or even, then she should hear it. In fact, he MUST have one surely? I spoke to a couple of parents this morning, & their kids had all done the homework, making the assumption that anything ending in 1, 3, 5 etc (regardless of whether there was a decimal) was odd. My DD got as far as the ones with decimals in & then brought it to me as she thought it was weird. She was saying "3.5 is the same as 3 and a half. How can that be odd or even?" If she can pose the question, he should be able to answer it, & if my answer's wrong (which he thinks it is) then he can't rely on me to explain it to her.

DD is aged 9 & has always been a bit geeky where maths is concerned. She's pretty good at maths (not genius wink ) & she finds it really fascinating. She won't accept an answer which says even numbers divide by 2, but 3.6 is an even number, because she can see that's just not logical. I guess I'm hoping that rather than lacking confidence in maths & teaching them wrong, he's actually fabulous at maths, I'm wrong, & by the end of the day he'll have given her an unamabiguous explanation of when odd & even can apply to numbers that aren't whole.

GooseyLoosey Mon 10-Oct-11 11:31:39

Surely by his analysis all numbers are even as you could represent 3 as 3.0 which would be an even number (as far as I understand his logic).

isitwineoclockyet Mon 10-Oct-11 11:35:09

GooseyLoosey -

I've just sent an email to my husband saying exactly that!


sparkle12mar08 Mon 10-Oct-11 11:36:48

You're too generous by half - HE'S WRONG! There's nothing you can do to change that, and therefore nothing you should avoid doing in bringing it up with the head. He's a bad teacher. Sorry!

isitwineoclockyet Mon 10-Oct-11 11:38:22

I'm hoping he's going to spend half his lunch break Googling it, & the other half going "Oh shit......"

schobe Mon 10-Oct-11 11:41:41

shock at crappy maths teaching.

isitwineoclockyet Mon 10-Oct-11 11:58:59

Perhaps I should just add that the homework was a photocopied Scholastic sheet, not something he'd written himself.

I have scoured the internet (& there are other things I really should be doing!) & can't find anywhere that explains how decimals can be odd or even.

He is talking crap isn't he?

I really can't talk to the head. Long, long story, but that is 100% not an option.

Am really pissed off but not sure what I can do.

witchwithallthetrimmings Mon 10-Oct-11 12:01:35

you really need to tell someone about this, the governers/PTA?

RosemaryandThyme Mon 10-Oct-11 12:13:00

Sounds like maths teacher has got into a tricky spot.
If its' too difficult to confrount teacher / head further, how about a little stealth, print off this thread or similar explinations from the web and pop under teachers car window wiper at collection time.

Catilla Mon 10-Oct-11 12:34:07

If the sheet was photocopied from somewhere, could you ask to see the source? Say you want to be able tounderstand the background in order to help your DD?

In your OP you said you asked "the school" - who was that? Is there a Head of Maths?

zipzap Mon 10-Oct-11 12:40:30

Ring up the school, see if there is a person responsible for maths teaching within the school, get their email or other contact details and see if you can speak to them or email them.

Even it it's just an emergency:
'I am exceedingly worried that my dd is being taught wrong information about odd and even numbers and it is making her confused. mr xx sent out homework about odd and even numbers that was mathematically wrong. When I tried to talk to him about it he not only dismissed my concerns but got the explanation wrong himself, showing that he doesn't know what he is supposed to be teaching his class.

Given that the basic definition of odd and even numbers [insert the useful definitions already given on here] is very clear cut, please could you ensure that it is explained properly to dd's class so they are not disadvantaged by the very confusing and wrong information they have been taught so far. Thank you'

And then arrange to go in to speak to them later if needs be...

I would also have written something on her homework to point out exactly where it was wrong. And I would also write to Scholastic to point out the HUGE error they are making in providing a work sheet like this. If it was difficult calculus or big differential equations then it's not good but everybody has a bad day and makes a typo or mistake. Or even about different ways of doing addition or subtraction etc that they don't want you to confuse kids by teaching them the proper the old fashioned way. But this is really basic maths that underpins lots of stuff and shouldn't be mis-taught. It's also really worrying that if they are getting this wrong then what other stuff are they not teaching correctly!

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