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 Post subject: One fifth of one eighth
PostPosted: Mon Oct 03, 2016 9:34 pm 
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Just want to ask all the current maths teachers how this kind of question is taught at secondary school. I have just been told it involves pizzas :-(


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PostPosted: Mon Oct 03, 2016 9:48 pm 
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Why pizzas? Could be anything .... the key is understanding that finding 1/5 of anything means division into 5 equal parts.


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PostPosted: Tue Oct 04, 2016 9:21 am 
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BucksBornNBred wrote:
Just want to ask all the current maths teachers how this kind of question is taught at secondary school. I have just been told it involves pizzas :-(



1/5 of 1/8. In Maths, of means multiplication
1/5 X 1/8 (multiply numerators, multiply denominators) = 1/40


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PostPosted: Tue Oct 04, 2016 9:29 am 
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That's not really teaching it ....


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PostPosted: Tue Oct 04, 2016 9:56 am 
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Guest55 wrote:
That's not really teaching it ....


The pizzas or the 'just how to do it'?

I don't think pizzas even existed in the parts of the UK where I least basic maths :shock: , so multiplying and dividing fractions was just taught 'straight'. I remember thinking it was kind of a 8) thing to know (but then, we didn't even have colour telly until Princess Anne's - first - wedding, not a huge amount of sophistication in our household).

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PostPosted: Tue Oct 04, 2016 9:59 am 
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Olucares response is 'how to do it' and is not really explaining why it works which is what I think 'teaching' is.


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PostPosted: Tue Oct 04, 2016 10:11 am 
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Using pizza, as suggested, I'd start by asking the child to draw a large pizza and then 'cut' it (by drawing lines) into 8 equal slices. So, we now have one eighth (of a pizza in this case) - i.e. one slice.

The question asks to find one fifth of one eigth, so I'd ask the child to cut one of the slices into 5 'slivers' of pizza. Hopefully the child would recognise that each of these slivers is one fifth of one eigth of the original (whole) pizza.

Then I'd ask what fraction of the pizza does one sliver represent? Or, put another way, if I cut the entire pizza into slivers of this same size, how many would I have? Hopefully the child would realise that if one slice has been cut into five slivers, but there are eight slices altogether, then they'd end-up with 5 x 8 slivers altogether.

Each sliver is therefore one fortieth of the whole pizza.

Personally, I often use the pizza analogy when discussing fractions with my DD, as I find the concept of a pizza box lends itself well to dealing with improper fractions.

(BTW, I realise that 'slice' and 'sliver' are not very mathematical terms, but we are talking pizza after all!)


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PostPosted: Tue Oct 04, 2016 10:17 am 
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Goodheart - yes they are good in KS2 - although personally I prefer other 'items' as it's hard to divide a pizza into eactly equal slices [sectors] ...


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PostPosted: Tue Oct 04, 2016 11:26 am 
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You could always use a tart instead of a pizza. Maybe a pork pie? But a bit chunky to imagine cutting it into 40ths- those slivers would just be a pile of crumbs and meat.

I wonder how many places in the UK still have not been exposed to the noble pizza?

I was not "taught" to do any maths by your definition, G55-just to memorize a bunch of meaningless rules. I really love the pizza-sort of lesson - I never actually understood a lot of maths until recently when trying to help my own kids. I think I would have enjoyed it a lot more.


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PostPosted: Tue Oct 04, 2016 11:47 am 
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I'm a big fan of the use of practical equipment - it disappears too quickly in KS2 in some schools.

The teaching of maths is so much more fun these days - what is the point of learning loads of 'rules' than make no sense and can never be applied to other contexts?

I would use something 'practical' but maybe not a pizza.


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