# Talk

## When are fractions used in real life

(74 Posts)
TeenTimesTwo Mon 05-Feb-18 20:49:56

I was asked today by a y6 I'm helping when fractions are used in real life. I struggled to answer it.

Now, I know we often want basic use like 'a third off'.
I also obviously know about percentages, probability and ratios.

But when 'in real life' do you have to add fractions with different starting denominators, or multiply mixed numbers or whatever?

LIZS Mon 05-Feb-18 20:52:12

Working out recipe quantities if written for 6 and you need to make it for 4.

VienneseFingers Mon 05-Feb-18 20:56:33

Luckily I have never had to add fractions with different starting denominators or multiply mixed numbers as I can't remember how to and had actually forgotten it was even a thing.

Biggreygoose Mon 05-Feb-18 20:56:33

Mixes. (Recipes, concrete, fuel etc etc)

If you fancy a splash on the gg's

In pretty much any engineering discipline.

VienneseFingers Mon 05-Feb-18 20:57:22

And I cook a lot and bet on horses...

Slitherout Mon 05-Feb-18 20:57:23

If you want to buy weed 😂

FATEdestiny Mon 05-Feb-18 20:57:55

There is three quarters of a cake left. There are four children, plus Mum and Dad. How much cake each?

TeenTimesTwo Mon 05-Feb-18 20:58:01

I'm disallowing that LIZS as it's for ratios and too basic.
It's just 4/6 x the quantity

I would like a harder use to help justify harder fractions work.

noblegiraffe Mon 05-Feb-18 20:58:38

I use them all the time

Yeah, not so much in 'real life' though. Probably one of those things that got used far more often back when we used imperial units and didn't have calculators. Old O-level papers are always full of horrible 'real life' fraction questions.

noblegiraffe Mon 05-Feb-18 20:59:55

help justify harder fractions work

Ah, now you're in the territory of thinking it needs to be useful to be taught. Dangerous in a maths lesson!

FATEdestiny Mon 05-Feb-18 21:01:59

We have 2 large pizzas cut into 12 plus 2 medium pizzas cut into 8. There are 10 of us. How can we all get a fair share?

TeenTimesTwo Mon 05-Feb-18 21:03:00

Fate - 3/4 div 6 - too easy.

Mixes - possibly, yes.
Betting, good example of something definitely.

I'm definitely not going to say when buying drugs!

I did say harder maths, and formulae, which I guess includes engineering.

Nice ideas. Any more involving different denominators?

MarthaArthur Mon 05-Feb-18 21:03:10

Measuring things in ratios. Or if she goes into mathmatic or science based jobs.

Biggreygoose Mon 05-Feb-18 21:04:33

Noble is right though, fractions were far more relevant under the imperial system.

fruitpastille Mon 05-Feb-18 21:05:14

It's hard to justify. Like long multiplication or division - I mean really who would do that on paper in real life? You need to have a sense of the value of the numbers and understand what the calculation does/is for so you realise when your calculator has made a mistake though.

TeenTimesTwo Mon 05-Feb-18 21:08:04

FATE I like that example, uses areas of circles too.

noble thinking it needs to be useful to be taught Ah I agree that could be dangerous. BUT it's nice if possible to show a real world application, and I couldn't think of one simple enough for an 11 yo off the top of my head and rather though there should be one.

Biggreygoose Mon 05-Feb-18 21:09:02

When you have to be horrifically precise in a calculation and ain't got time to write that shit down.

Very much depends how you define 'real life's ...

TeenTimesTwo Mon 05-Feb-18 21:11:43

fruit I often(ish) do long multiplication or division as it's faster than getting a calculator!

There wasn't any attitude from the child ('why do I need to do this' moaning), just an interested question.

You'll need it for harder maths is a good enough answer.

liloland Mon 05-Feb-18 21:12:49

Splitting the bill when dining with people who do that kind of thing.

TeenTimesTwo Mon 05-Feb-18 21:18:34

Surely not bill splitting, we're not on AIBU.

Anyway, either divide by the number of people, or people pay for their own, or divide and adjust up and down a bit to allow for variation.

noblegiraffe Mon 05-Feb-18 21:19:41

I've been banging on about using fractions to my Y10s recently, we've been doing completing the square and some are insisting on using decimals. I've been arguing that it's much easier to square a fraction than it is a decimal. I'll win that one eventually.

You could wind the class up by having a project to see what

1+1/2+1/3+1/4+.... all the way adds up to.

Divergent series for junior school. Then you could get them to do the inverse squares sum on a calculator and appear godlike by getting then to see how close to Pi^2/6 they can get. Much more exciting than real life!

titchy Mon 05-Feb-18 21:28:47

Estimating how much carpet you need to buy, converting currencies, sales shopping - is it really a bargain, converting imperial to metric, engineering - loads of examples from thickness of a steel to measuring traffic flow.

TeenTimesTwo Mon 05-Feb-18 21:31:09

rogue You could wind the class up
Not me. Not a teacher. Could never be a teacher. All those kids in one go? Couldn't cope.

ClaudiaWankleman Mon 05-Feb-18 21:32:13

When doing taxes. You could easily be multiplying % and fractions in the same calculations as a bookkeeper.

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