About cookies

The NCETM site uses cookies. Read more about our privacy policy

Please agree to accept our cookies. If you continue to use the site, we'll assume you're happy to accept them.

 

Personal Learning Login






Sign Up | Forgotten password?
 
Register with the NCETM

Secondary Magazine - Issue 33: An idea for the classroom


This page has been archived. The content was correct at the time of original publication, but is no longer updated.
Created on 29 April 2009 by ncetm_administrator
Updated on 15 May 2009 by ncetm_administrator

Secondary Magazine Issue 33  
 

An idea for the classroom - perimeter

In Issue 31, I talked about an article in ‘Mathematics Teaching’ 211 – November 2008 written by John Mason. Included in the article are some activities which are ‘designed to promote work on the awareness which underpin perimeter and area’. 
Following on from John’s ideas, I was inspired to do some more work on perimeter.

The resource shows a rectangle.
If you know the length and width of the rectangle it is possible to work out the perimeter. If the length and width are a and b, the perimeter is 2a + 2b. Similarly, if indents are made to the rectangle, the perimeter can still be expressed in terms of a and b.

The resource goes on to show progressively more complicated shapes, each derived from the previous one, whose perimeters can be expressed in terms of the original length and width.

Having used the shapes on the resource, students can be asked to draw their own rectangle and progressively modify the shape, at each stage determining the new perimeter in terms of the original. Using your own starting point and making your own modifications is an integral part of the activity rather than a ‘bolt on’ for those that finish quickly.

Good questions to ask pupils would be:

  • How does your new shape relate to your original shape?
  • Is the width of the indent important?
  • Is the length of the indent important?
  • Can you draw a shape whose perimeter is 4a + 2b, etc.
  • Can you draw a shape whose perimeter is 3a + 2b, etc.

Although pupils calculate the perimeter of the shape, the main focus is to use mathematical reasoning to justify the decisions the pupils make in order to perform the calculations.

Have you got a nice activity to reinforce pupils’ understanding of perimeter? Why not tell us about it?
 

 
 
 Click here to view this issue in PDF format
 
 Visit the Secondary Magazine Archive
 
 About Magazine feeds
 
 
 Previous page
Next page 
 
 
 Back to top

 
 
 

Quicklinks

 
Secondary Magazine Issue 33 - Click here to download as a PDF
 
 
Magazine Feed - keep informed of forthcoming issues
 
Departmental Workshops - Structured professional development activities
 
Explore the Secondary Forum
 
Contact us - share your ideas and comments 

Comment on this item  
 
Add to your NCETM favourites
Remove from your NCETM favourites
Add a note on this item
Recommend to a friend
Comment on this item
Send to printer
Request a reminder of this item
Cancel a reminder of this item

Comments

 


There are no comments for this item yet...
Only registered users may comment. Log in to comment