99% of people answer this question wrong! The best counting triangles starter ever!

99% of people answer this question wrong! The best counting triangles starter ever!
Woman looks through triangle made with her fingers

The best triangles counting starter solution

The documents needed for this engaging counting triangles starter can be downloaded below. We have all seen these counting shape type activities doing the rounds on Facebook and Twitter and we are all aware of how much discussion that they create on these social networking sites, subsequently, I decided to use them as a starter within my lessons.

The PowerPoint that can be downloaded below is a proof for use with the starter. I find that students are happy to accept the PowerPoint as the correct answer due to the simple visuals of overlaying different coloured triangles. I have also included a Microsoft Word document which has these triangles as a template; I cut them up and give one to each student so that they can use them to help them count. On the PowerPoint there is the following lesson’s starter which is another counting triangles activity, I find the students are much better at this second one because of the techniques and strategies that they have developed during the previous lesson.

Counting Triangles Starter

The type of questions and thought provoking statements to raise further questions that are I make are along the lines of:
  • Should it be an odd or even number?
  • There is one big triangle, so does this make the total odd or even?
  • Do overlapping triangles count?
  • Different orientations of shapes – are they still triangles?
  • Is there a repeating pattern to make the counting easier?
  • What methods of counting are used?
  • How can you be systematic to ensure that you do not count twice or miss some.
  • What if we added another row to the overall shape, how much would this increase the total number by?
  • Can you estimate a total and then check this?
Let me know how you get on as feedback is always appreciated. If you think of any other questions that we can ask the students, or questions raised by the students themselves, please let me know and I will add them to the list. I have many more of these counting triangle activities, along with others that involve counting squares and rectangles, so if there is enough demand I will include them within my next blog.
Here is a powerpoint of the solution;

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3 comments on “99% of people answer this question wrong! The best counting triangles starter ever!
  1. Boz says:

    I count at least 24!

  2. Anon says:

    Ooop!!! After I saw the power point I got the missing one. It is 27. Thanks.

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