Cross Perimeter

50cm

55cm

Calculate the distance around this shape. All angles are right angles but the diagram is not drawn to scale.

Show Hint

A Mathematics Lesson Starter Of The Day


Topics: Starter | Geometry | Mensuration

  • Mr Wheldon, Springwood Heath
  •  
  • Shayne got this in 5 seconds!!!
    Well done.
  • Mandy Smith, Anderton Park
  •  
  • Please, please would you include the answers!!
    [Mandy, the answers are further down this page but only appear for teachers when they are logged in - Transum]
  • Sergio R., Colombia.
  •  
  • It is really nice to comment and notice that you can reduce the area an the perimeter will be the same, in the infinite you will have a cross without area.
  • Transum,
  •  
  • That's a very interesting observation Sergio. What we really need is an animation to show that. It is not intuitive for most people to realise that you can increase or decrease the area of a shape while keeping the perimeter the same.

    There was a similar Starter last October called Stair Perimeter. Underneath the diagram is a button labelled 'Show Hint'. Click the button to show an animation that should make the situation clear.

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.
Click here to enter your comments.

Previous Day | This starter is for 9 February | Next Day

 

Answer

Sign in to your Transum subscription account to see the answers

Extension

If all of the vertical edges are the same length and all of the horizontal edges are the same length, what is the area of the shape?




Your access to the majority of the Transum resources continues to be free but you can help support the continued growth of the website by doing your Amazon shopping using the links on this page. Below is an Amazon link. As an Amazon Associate I earn a small amount from qualifying purchases which helps pay for the upkeep of this website.

Educational Technology on Amazon

 

Online Maths Shop

Laptops In Lessons

Teacher, do your students have access to computers such as tablets, iPads or Laptops?  This page was really designed for projection on a whiteboard but if you really want the students to have access to it here is a concise URL for a version of this page without the comments:

Transum.org/go/?Start=February9

However it would be better to assign one of the student interactive activities below.

Laptops In Lessons

Here is the URL which will take them to a related student activity.

Transum.org/go/?to=areacomposite

Student Activity

 



 

Extension Answer

Curriculum Reference

See the National Curriculum page for links to related online activities and resources.

Apple

©1997-2022 WWW.TRANSUM.ORG