Perimeter and Area

Students learn how to find the perimeter and area of various 2D shapes including triangles, quadrilaterals, compound shapes and circles.  Throughout the topic links are made to algebraic reasoning and estimation.  This topic takes place in Term 4 of Year 9 and links to arc length and area of sectors later on.


Perimeter and Area Lessons
Revision Lessons

Prerequisite Knowledge

  • choose and use appropriate standard units to estimate and measure length/height in any direction (m/cm); mass (kg/g); temperature (°C); capacity (litres/ml) to the nearest appropriate
  • unit, using rulers, scales, thermometers and measuring vessels
  • compare and order lengths, mass, volume/capacity and record the results using >, < and =
  • measure, compare, add and subtract: lengths (m/cm/mm); mass (kg/g); volume/capacity (l/ml)

Success Criteria

know and apply formulae to calculate:

  • rectangles
  • rectilinear composite shapes
  • area of triangles
  • parallelograms
  • trapezia

calculate the perimeters of 2D shapes, including composite shapes;

Key Concepts

  • Perimeter is a measure of length around the outside of a shape whereas area is the space on a surface.
  • Students should be given the opportunity to derive formulae to calculate the area and perimeter of shapes.
  • Area is measured in square units.
  • Demonstrate a triangle as being half a rectangle so students know to use the perpendicular height in their calculation.
  • Demonstrate a parallelogram as having an equal area to a rectangle.
  • To calculate the area of composite rectilinear shapes have students break them up in different ways.

Common Misconceptions

  • Students often confuse area and perimeter.
  • Students can forget to include correct units when stating an area or perimeter.
  • When calculating the area of a triangle or parallelogram students tend to use the slanted height rather than the correct perpendicular height.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes:

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Mr Mathematics Blog

Literacy in Mathematics – Creating Problem Solvers

Last year my school had a OFSTED trial inspection. Whilst the maths team recieved favourable feedback the inspectors noted a need for a focus on whole school literacy. Because of this I was asked to demonstrate how we develop student’s literacy in mathematics. Literacy in Mathematics By developing student’s literacy in mathematics we aim to […]

Angles in Polygons

There are two key learning points when solving problems with angles in polygons.  The first is to understand why all the exterior angles of a polygon have a sum of 360°.  The second is to understand the interior and exterior angles appear on the same straight line. Students can be told these two facts and […]

Getting Ready for a New School Year

When getting ready for a new school year I have a list of priorities to work through. Knowing my team have all the information and resources they need to teach their students gives me confidence we will start the term in the best possible way.  Mathematics Teaching and Learning Folder All teachers receive a folder […]