Following on from last week’s theme of irregular polygons and perimeters, this week’s #MondayMaths tackles a selection of even stranger shapes with some trusted squared paper.
It’s half term now, so we’ll all be moving into Autumn 2 next week. Our Year 7 mastery students will be looking at calculating areas of rectangles and triangles. On the strength of that skill and knowledge, this puzzle challenges their ability to recognise composite shapes and create strategies for calculating their areas.
Starting from the basics
As we can see, all the shapes above are built on combinations of rectangles and triangles, including the subtraction of triangles and rectangles.
Here’s an example showing how this shape can be visualised as a triangle subtracted from a rectangle to create a new irregular polygon:
Can you explain why?
This problem is a great opportunity for students to explore geometric calculation strategies and explain their decisions using correct mathematical language.
*Note the question asks students to sort the shapes into groups with the same area, so once a student has found the area of one shape, it might be worth trying to immediately hypothesise which of the other shapes share that area.
Remember to encourage students to explain their reasoning, and to check their hypothesis through calculation.
Extending the exercise
Which polygon puzzle did you prefer – this one or last week’s? Let us know on Twitter where you can find the answer on Thursday.Back to news list Next article