Go to navigation
It is currently Thu Dec 08, 2016 7:57 am

All times are UTC




Post new topic Reply to topic  [ 12 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: Sun Jun 19, 2016 5:49 am 
Offline

Joined: Mon Jul 27, 2015 6:44 am
Posts: 488
https://occupymath.wordpress.com/2016/0 ... fractions/

I am feeling really thick as was never taught to compare fractions by cross- multiplying.
This is brilliant and am going to teach this to DD's as soon as they wake up - it would have been so useful for all those ordering fractions questions on the 11+ !
Was anyone else taught this?


Top
 Profile  
 
PostPosted: Sun Jun 19, 2016 8:25 am 
Offline

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11949
Sorry - what is good about their suggested method? Please don't teach this!

What makes them an authority on teaching fractions?

The way to compare fractions IS to make common denominators - that is the basis of understanding what a fraction is.

You cannot use their method if you have more than two fractions to compare ....


Top
 Profile  
 
PostPosted: Sun Jun 19, 2016 9:20 am 
Offline

Joined: Sat Aug 10, 2013 11:46 am
Posts: 188
I too thought the cross multiplication thing was very neat.

However, skip reading the document he was so much against, I thought it was quite good. I remember drawing lots of very similar things out for my daughter when teaching fractions. In my book, the more diagrams the better. A picture is so much more interesting for a child than writing and does help build their understanding if they can "see" why they are doing things. Lots of bright colours helps.

I find, as her understanding has built, the diagrams are not needed and so she would now simply be writing the sum out to find equivalents.

I still use diagrams on other things. For instance, in completing the square, I would draw out a square of length x+b, so she could see the b^2 bit she was taking away.

Famously even Richard Feynman was not adverse to drawing diagrams.


Top
 Profile  
 
PostPosted: Sun Jun 19, 2016 9:44 am 
Offline

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11949
Anyone that has studied teaching and learning maths knows the problems cross multiplying can lead to - that's why it's never taught as a technique.

Understanding is the key to learning maths - fractions are a difficult concept and 'short-cuts' lead to error. There's been lots of research on teaching fractions ...


Top
 Profile  
 
PostPosted: Wed Jun 22, 2016 1:36 pm 
Offline

Joined: Mon Jun 13, 2016 11:43 am
Posts: 10
It will be much simpler for children to learn fundamentals of fractions using LCM of denominators approach that can be applied to add, subtract or compare 2 or more fractions, rather than a technique which can only be applied to compare only 2 fractions at a time.

You can teach them techniques or short cuts, once they have strong understanding of core concepts.


Top
 Profile  
 
PostPosted: Wed Jun 22, 2016 3:23 pm 
Offline

Joined: Sat Jul 24, 2010 9:45 pm
Posts: 1488
From the article quoted by OP:
Quote:
One of them said “You cannot teach kids to cross-multiply because then they will do it everywhere, like when they are trying to add fractions”. Occupy Math thinks this is very close to “You cannot teach people to use screwdrivers because they will try to use them to tighten bolts or stir coffee.”

Believe it or not, I did witness a window-fitter stirring his coffee with a screwdriver... :lol:

_________________
It felt like I hit rock bottom; suddenly, there was knocking from beneath... (anon.)


Top
 Profile  
 
PostPosted: Thu Sep 01, 2016 8:48 pm 
Offline

Joined: Fri May 20, 2016 9:55 am
Posts: 27
booellesmum wrote:
https://occupymath.wordpress.com/2016/06/17/how-not-to-teach-fractions/

I am feeling really thick as was never taught to compare fractions by cross- multiplying.
This is brilliant and am going to teach this to DD's as soon as they wake up - it would have been so useful for all those ordering fractions questions on the 11+ !
Was anyone else taught this?



I completely agree that this is a brilliant method!


Top
 Profile  
 
PostPosted: Thu Sep 01, 2016 8:56 pm 
Offline

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11949
olucares wrote:
I completely agree that this is a brilliant method!


It doesn't work for more than two fractions - please read the other posts about why it is not taught.


Top
 Profile  
 
PostPosted: Thu Sep 01, 2016 9:01 pm 
Offline

Joined: Thu Mar 12, 2015 4:11 pm
Posts: 173
Don't see what's wrong with simply identifying common denimators and the comparing numerators.


Top
 Profile  
 
PostPosted: Thu Sep 01, 2016 9:36 pm 
Offline

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11949
The OP was suggesting cross-multiplying which is not a good method.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ]  Go to page 1, 2  Next

All times are UTC


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
CALL 020 8204 5060
   
Privacy Policy | Refund Policy | Disclaimer | Copyright © 2004 – 2016