During my years of teaching, I always realise one obvious but constantly made mistake among my students when they attempt this topic that involves figures, circles and triangles… yes, Area & Perimeter.
Many a times, my students feel that they are similar because both formulas require the use of length and breadth (for Squares/Rectangles), base and height (for Triangles), radius and π (for Circles). The tricky part that many fellow educators and parents face is that it is difficult to explain to their children or students that Area and Perimeter are related yet different in their own ways.
My students always tell me this:
“Mr. Marc, they both use breadth and length! (for a rectangle) They are the same right?”
“Mr. Marc, area and perimeter have the ‘same’ units! Only area does not have the ‘2’ on top!”
I am sure this sounds familiar to many of you.
This always tells me one thing…my students only know the formulas for area and perimeter by memorising it. They do not understand how this concept correlates to one another. This can make the difference between scoring 5 marks or 0 marks in a problem sum.
Here’s a simple yet effective trick that I use to explain this confusing situation to my students.
Imagine you are a farmer today…
Area is the amount of space you have to plant crops (i.e. vegetables, carrots, etc.)
This is the amount of space in the field that I have to plant my crops. Many students mistake area as a length. By knowing that it is the amount of space inside a field, my students tell me that this helps them recall easily the concept that area is a space, and not a length. Thus, area being a space reminds them that units would have to be in cm2 / m2.
Now comes the confusing part about Perimeter and why it is different from Area!
Perimeter is the distance that I have to run around the field. (No taking of shortcuts here!)
No matter what the given figure is, here are the steps to minimize missing out any sides of the figures when finding the perimeter.
Step 1 : Mark out with an ‘X’ a start point
Step 2: From the ‘X’, imagine you are running around the field (figure) with no shortcuts to be taken in a clockwise manner
Step 3: When you arrive back at the ‘X’, this means you have completed running around the field arriving back at your start point.
Simple right? :)
This also helps my students from missing any sides and ensures that they have covered all ‘ground’ along the path of the figure. With this, my students are normally able to tell me now that Perimeter is a distance and hence, the units are in cm / m .
Give it a try and let me know if you face any problems!
I hope this resource has been useful for you and your child as it has been useful for my students. Do feel free to drop me a comment below if you have any questions or need any clarifications that you need. Your question might be of help to others too !
To allow your child to have an easier time recalling these tricks, I have created a FREE Revision Card which I am giving away. Simply join our mailing list now to download the FREE Revision card and other learning resources in the future!