The Isle of Calculasia in #MondayMaths

Blog: Vicki Robinson , Communications Officer | Posted: 26/09/16
The Isle of Calculasia in #MondayMaths

Welcome to the Isle of Calculasia… a brilliant brain teaser for applying knowledge of perimeters and fractions. This week’s #MondayMaths puzzle shows three adjacent countries on a fictional island with their individual perimeters and borders between each country.

We’re asking puzzle-solvers to find the perimeter of the entire island from the information given.

At the beginning of the Autumn term, Year 7 students work with the application of addition and subtraction to find perimeters of simple polygons. And in Year 8, students should become confident with adding and subtracting fractions.

Wobbly perimeters

While students will be more used to identifying the lengths of straight-line edges that form perimeters of shapes, we’ve shaken things up a bit with non-linear edges.


More obviously than with some maths puzzles, a large part of this task is about spotting how to identify the information you need – and most importantly being able to add and subtract fractions of different denominators.

So far, we know D and E and “A+D”, “C+E” and “B+D+E” but we need to find “A+B+C”.

We’re working with mixed fractions in this problem but students can decide whether their understanding of how to convert between mixed and improper fractions (from Spring 2 of Year 7) might help them here.

Team work

This problem requires a systematic approach with multiple steps to obtain a solution. As reaching the final solution relies on having correct answers at every step, we encourage students to talk to each other about the maths as they work through the problem to confirm that their answers are the same.

Don’t forget to check our Twitter page on Thursday for the answer – and let us know how you got on!

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