List

Angles, Polygons and Geometrical Proof (age 11-14)

This is part of our Secondary Curriculum collection of favourite rich tasks arranged by topic.

Scroll down to see the complete collection, or explore our subcollections on Perimeter and Area in two dimensions, and Surface Area and Volume in three dimensions.

Polygon Pictures
problem
Favourite

Polygon Pictures

Age
11 to 14
Challenge level
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Can you work out how these polygon pictures were drawn, and use that to figure out their angles?

An Equilateral Triangular Problem
problem
Favourite

An Equilateral Triangular Problem

Age
11 to 14
Challenge level
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Take an equilateral triangle and cut it into smaller pieces. What can you do with them?

Angles inside
problem
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Angles inside

Age
11 to 14
Challenge level
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Draw some angles inside a rectangle. What do you notice? Can you prove it?
Parallelogram It
problem
Favourite

Parallelogram It

Age
11 to 16
Challenge level
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Players take it in turns to choose a dot on the grid. The winner is the first to have four dots that can be joined to form a parallelogram.

Quadrilaterals game
game
Favourite

Quadrilaterals game

A game for 2 or more people, based on the traditional card game Rummy.
Tilted Squares
problem
Favourite

Tilted Squares

Age
11 to 14
Challenge level
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It's easy to work out the areas of most squares that we meet, but what if they were tilted?
Square It
problem
Favourite

Square It

Age
11 to 16
Challenge level
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Players take it in turns to choose a dot on the grid. The winner is the first to have four dots that can be joined to form a square.

Triangles in circles
problem
Favourite

Triangles in circles

Age
11 to 14
Challenge level
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Can you find triangles on a 9-point circle? Can you work out their angles?

Semi-regular Tessellations
problem
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Semi-regular Tessellations

Age
11 to 16
Challenge level
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Semi-regular tessellations combine two or more different regular polygons to fill the plane. Can you find all the semi-regular tessellations?

Cyclic Quadrilaterals
problem
Favourite

Cyclic Quadrilaterals

Age
11 to 16
Challenge level
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Draw some quadrilaterals on a 9-point circle and work out the angles. Is there a theorem?
Hidden Squares
problem
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Hidden Squares

Age
11 to 14
Challenge level
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Can you find the squares hidden on these coordinate grids?
Guess \my Quad
problem
Favourite

Guess my Quad

Age
11 to 14
Challenge level
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How many questions do you need to identify my quadrilateral?

Polygon Rings
problem
Favourite

Polygon Rings

Age
11 to 14
Challenge level
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Join pentagons together edge to edge. Will they form a ring?

Completing Quadrilaterals
problem
Favourite

Completing Quadrilaterals

Age
11 to 14
Challenge level
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We started drawing some quadrilaterals - can you complete them?

Star Polygons
problem
Favourite

Star Polygons

Age
11 to 14
Challenge level
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Draw some stars and measure the angles at their points. Can you find and prove a result about their sum?
Rhombus It
problem
Favourite

Rhombus It

Age
11 to 16
Challenge level
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Players take it in turns to choose a dot on the grid. The winner is the first to have four dots that can be joined to form a rhombus.

Square coordinates
problem
Favourite

Square coordinates

Age
11 to 14
Challenge level
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A tilted square is a square with no horizontal sides. Can you devise a general instruction for the construction of a square when you are given just one of its sides?

Subtended angles
problem
Favourite

Subtended angles

Age
11 to 14
Challenge level
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What is the relationship between the angle at the centre and the angles at the circumference, for angles which stand on the same arc? Can you prove it?
Right angles
problem
Favourite

Right angles

Age
11 to 14
Challenge level
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Can you make a right-angled triangle on this peg-board by joining up three points round the edge?
Shapely pairs
problem
Favourite

Shapely pairs

Age
11 to 14
Challenge level
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A game in which players take it in turns to turn up two cards. If they can draw a triangle which satisfies both properties they win the pair of cards. And a few challenging questions to follow...

Property chart
problem
Favourite

Property chart

Age
11 to 14
Challenge level
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A game in which players take it in turns to try to draw quadrilaterals (or triangles) with particular properties. Is it possible to fill the game grid?

Opposite vertices
problem
Favourite

Opposite vertices

Age
11 to 14
Challenge level
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Can you recreate squares and rhombuses if you are only given a side or a diagonal?

Quadrilaterals in a Square
problem
Favourite

Quadrilaterals in a Square

Age
11 to 14
Challenge level
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What's special about the area of quadrilaterals drawn in a square?
Which solids can we make?
problem
Favourite

Which solids can we make?

Age
11 to 14
Challenge level
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Interior angles can help us to work out which polygons will tessellate. Can we use similar ideas to predict which polygons combine to create semi-regular solids?
Of all the areas
problem
Favourite

Of all the areas

Age
14 to 16
Challenge level
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Can you find a general rule for finding the areas of equilateral triangles drawn on an isometric grid?


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Angles, Polygons Stage 3 STEM footer
 

You may also be interested in this collection of activities from the STEM Learning website, that complement the NRICH activities above.