Triangles

problem

Ratty

Age

11 to 14

Challenge level

If you know the sizes of the angles marked with coloured dots in this diagram which angles can you find by calculation?
problem

Circumnavigation

Age

14 to 16

Challenge level

The sides of a triangle are 25, 39 and 40 units of length. Find the diameter of the circumscribed circle.
problem

Parallelogram in the Middle

Age

11 to 14

Challenge level

Weekly Problem 27 - 2013
The diagram shows a parallelogram inside a triangle. What is the value of $x$?
problem

Equal Lengths

Age

11 to 14

Challenge level

Weekly Problem 29 - 2013
An equilateral triangle is drawn inside a rhombus, both with equal side lengths. What is one of the angles of the rhombus?
problem

Half a Triangle

Age

14 to 16

Challenge level

Construct a line parallel to one side of a triangle so that the triangle is divided into two equal areas.
problem

Wedge on Wedge

Age

14 to 16

Challenge level

Two right-angled triangles are connected together as part of a structure. An object is dropped from the top of the green triangle where does it pass the base of the blue triangle?
problem

Altitude Inequalities

Age

14 to 16

Challenge level

Weekly Problem 8 - 2010
Are you able to find triangles such that these five statements are true?
problem
Favourite

Paper Patchwork 2

Age

5 to 7

Challenge level

Have a go at making a few of these shapes from paper in different sizes. What patterns can you create?
problem
Favourite

Let's Investigate Triangles

Age

5 to 7

Challenge level

Vincent and Tara are making triangles with the class construction set. They have a pile of strips of different lengths. How many different triangles can they make?
problem

Seven Sticks

Age

5 to 7

Challenge level

Explore the triangles that can be made with seven sticks of the same length.