# The Great Dodecahedron

## What can you see hidden in plain sight?

This hexagon-shaped collection of triangles looks as though it could be a three-dimensional solid. Click triangles to hide them and double click to bring them back in order to complete the challenges below:

 1 Remove some triangles to leave an equilateral triangle in the centre. Check ✓ ✗ 2 Remove some triangles to leave a kite with a vertical line of symmetry. Check ✓ ✗ 3 Remove some triangles to leave an irregular pentagon containing the three pink pieces. Check ✓ ✗ 4 Remove some triangles to leave what looks like a tetrahedron viewed from above. Check ✓ ✗ 5 Some people see the whole design as a cube. Remove some triangles to show the top of the cube. Check ✓ ✗ 6 Remove all the pairs of triangles that prevent the design having a vertical line of symmetry due to their colours. Check ✓ ✗ 7 Remove some triangles to leave what looks like a star on a blue pentagon. Check ✓ ✗ 8 Remove some triangles to leave what looks like a star on a light green pentagon. Check ✓ ✗ 9 Remove some triangles to leave what looks like a star on a dark green pentagon. Check ✓ ✗

## Instructions

Try your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help.

When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file.

## More Activities:

Mathematicians are not the people who find Maths easy; they are the people who enjoy how mystifying, puzzling and hard it is. Are you a mathematician?

Comment recorded on the 3 October 'Starter of the Day' page by Fiona Bray, Cams Hill School:

"This is an excellent website. We all often use the starters as the pupils come in the door and get settled as we take the register."

Comment recorded on the 12 July 'Starter of the Day' page by Miss J Key, Farlingaye High School, Suffolk:

"Thanks very much for this one. We developed it into a whole lesson and I borrowed some hats from the drama department to add to the fun!"

Each month a newsletter is published containing details of the new additions to the Transum website and a new puzzle of the month.

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#### Car Park Puzzle

Can you get your car out of the very crowded car park by moving other cars forwards or backwards? There are five levels of increasing difficulty and the interactive interface makes this a fun problem solving exercise.

There are answers to this exercise but they are available in this space to teachers, tutors and parents who have logged in to their Transum subscription on this computer.

A Transum subscription unlocks the answers to the online exercises, quizzes and puzzles. It also provides the teacher with access to quality external links on each of the Transum Topic pages and the facility to add to the collection themselves.

Subscribers can manage class lists, lesson plans and assessment data in the Class Admin application and have access to reports of the Transum Trophies earned by class members.

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## Go Maths

Learning and understanding Mathematics, at every level, requires learner engagement. Mathematics is not a spectator sport. Sometimes traditional teaching fails to actively involve students. One way to address the problem is through the use of interactive activities and this web site provides many of those. The Go Maths page is an alphabetical list of free activities designed for students in Secondary/High school.

## Maths Map

Are you looking for something specific? An exercise to supplement the topic you are studying at school at the moment perhaps. Navigate using our Maths Map to find exercises, puzzles and Maths lesson starters grouped by topic.

## Teachers

If you found this activity useful don't forget to record it in your scheme of work or learning management system. The short URL, ready to be copied and pasted, is as follows:

Alternatively, if you use Google Classroom, all you have to do is click on the green icon below in order to add this activity to one of your classes.

It may be worth remembering that if Transum.org should go offline for whatever reason, there is a mirror site at Transum.info that contains most of the resources that are available here on Transum.org.

When planning to use technology in your lesson always have a plan B!

Transum,

Thursday, February 11, 2016

"The Great Dodecahedron poster was used to great effect on the Using and Applying Mathematics courses for teachers provided by Birmingham's Curriculum Support Service back in the day when Using and Applying Maths was seen to be a new concept!"

Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for those learning Mathematics anywhere in the world. Click here to enter your comments.

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