Feeling stupid - found my 6 year old's maths homework far from easy!

[TeaTime]

Some time ago there was a story about David Beckham not being able to do Brooklyn's homework and I read with smug amusement assuming that DB was mathematically challenged. I don't feel that way at all (Grade A Maths O level and all that....) BUT last night my dh worked with our ds on his homework (Y2) which looked simple enough but got us both bemused . Can any REAL mathematicians out there explain what the aim is? My frustration was not knowing what the formula would be for a 'right' answer (the joy of maths to me was that it had definite answers that could be checked).

Here is the problem: You have the choice of sandwiches, apple, crisps, chocolate bar or yoghurt. Only three things are allowed in the lunch box. How many days would you get a different lunch? It took me a while (resorting to ABCDE and writing down the possibilities) to decide it was 10 but dh thought 11. Ds quite happily just did 7 (the days of the week)...Anyone know the formula?

I'm starting to worry that my maths is way out of line with current approaches!! Is it OK that ds just found a few and didn't worry whether he had got all the combinations? That seems too 'loose' to me!

God I struggled with some year 4 mathis homework the other day. i could do it but struggled to explain to dd1 in a simple manner how she could do it.

I would recommend you pop in to see the teacher and ask that he/she put an example answer at the top of the homework. I always try to do this now I teach Y5) as children often cannot recall exactly what they have been taught when it comes to settling down to homework. There could also be a place for your child's school to offer a numeracy workshop to show parents what goes on in the numeracy hour. I'm sure your maths skills are more than adequate so don't worry.

I think the idea with this sort of homework in Y2 is for them to learn how to work something out logically and work out all the combinations - I don't think they're expected to use a formula at this stage.

So you would start by listing all the possibilities with sandwiches in them, which is what you did. If you've got it right, each ingredient appears the same number of times.

It is very tricky for young children to do it in an ordered way. DS2, who is 7 in Y3, had some homework that involved working out all the possible combinations of numbers you could make from 4 digits, then 5 digits, and he still tends to do it somewhat randomly.

Well, I made it 10 too!

DD is in year 5 and her first week's homework was what singersgirl's ds had to do in Y3 - I was shocked because I thought it was too easy for her now.

I remember in Year 1 dd having to do something like this, though. My bro (who is a mathematician) hates the fact that they are taught like this - he says "why can't they just use numbers!" despairingly and throwing his hands in the air!

Yes, I made it to 10 as well, and each ingredient appears 6 times!

Phew - glad we agree the answer, and I think that 6 is significant but not sure how / why - is it because you're allowed 3 items...?

Thanks for the advice ChipButty and the explanation of what the point is singersgirl... I didn't think they'd wanted him to know a formula but for my own satisfaction I was interested.

Actually if the point is making orderly combinations then the 5 random items makes this quite hard - I can see that the 4 digit and 5 digit exercise would be more straightforward somehow and more satisfying.

Anyway it's an interesting task for 'differentiation' where the real whizz kids can find the formula or work out a system and the rest just happily make random lunch boxes.. but I'm not sure what they get out of it if it IS just random as far as they can see - don't they get the feeling that maths tasks require random answers so guessing wildly is fine??!

answer 1

If its a healthy eating school, the crisps and the chocolate would not be allowed

That does sound quite hard for year 2! I am sure when I was that age we just did simple addition/subtraction sums.

The day you get crisps, chocolate and yoghurt - yummy

LOL purpleduck!

It's 5 x 4 x 3 - the number of choices you have for each 'slot' in the lunchbox.

So that's 60 different combinations.

But the order doesn't matter (ie crisps, chocolate and yogurt is no different to crisps, yogurt and chocolate etc).

So you have to remove all the duplicates, each combination of ingredients can appear in 6 (3 x 2 x 1) different orders.

60 / 6 = 10

Oof, that made my brain hurt (and I have maths A-level!)

It's quicker to work it out if you think about what you're leaving out rather than what you're including.

If you can include 3 items out of 5, that means you need to leave out 2 out of 5.

Say you leave out sandwiches, there are 4 other things you can leave out with them.

So 4 possibilities x 5 ingredients.

Gives you 20 - but that will include each combination in both orders.

So half it to get 10.

Message withdrawn

A long time later checking back and very pleased to find some real maths to explain why 10 is the right answer - thanks DCMB and LS!! I agree that all this is brain-aching stuff, not what you expect at Primary level!!

To be honest with you, I've set a similar task for Yr 2 homework and I didn't care what the answer was. I set it to encourage the children to practice working out in a systematic order

Hi CandleQueen - I can see that that was the main idea but what worries me is that when a task is so difficult that adults struggle then you will only get random answers from children and they will get the message that that is OK. Far from learning to be systematic they learn to be random! I can't see the point in giving a task that is practically impossible for the age it is set. What about children who are very bright and really WANT to do it systematically - how can they be helped to do so without introducing some sort of numbering or lettering to help? Why not just start with letters or numbers and give everyone a head start?

I'm not a primary teacher (did 18 months as a Section 11 teacher in the early 90s though) so I don't want it to look like criticism but I must admit it was a shock that maths had changed the 'rules' so much... Someone somewhere must be advising teachers to set these tasks but I personally can't see why.

It's permutations and combinations from the old O-level syllabus.

I think it all depends on what they do with the answers provided by the children when they get them. Whether the children get the message that random answers are OK or not depends on how those random answers are tackled.

And this way it sparks the curiosity of the children who are very bright -- they can start to wonder about other combinations and maybe do some investigations so that when the formal mathematics of the situation is introduced it will mean something to them.

I think that it is a good question because it gets the DC to think. IMO the thinking and reasoning behind it is more important than the correct answer.