Test
Triangles. Types of triangles.
This test classifies triangles by their sides and angles. Pupils identify equilateral, isosceles and scalene triangles, distinguish acute, right and obtuse triangles and apply their defining properties.
Time left: 00:00:00
Sample questions
- The drawing shows a triangle, mark its type.
- Two angles of a triangle are ___° and ___°. What is the third angle?
- The side lengths of a triangle are ___ cm, ___ cm and ___ cm. What type of triangle is it by sides?
- A triangle has sides ___ cm, ___ cm and ___ cm. What is its perimeter?
- A triangular garden bed has sides ___ m, ___ m and ___ m. How many metres of fence are needed around it?
Classifying triangles by sides and angles
A triangle has three sides, three vertices and three angles. It can be classified in two independent ways: by side lengths and by angle sizes. The same triangle receives one name from each group, so a triangle can be both isosceles and right-angled.
Classification by sides
- An equilateral triangle has three equal sides.
- An isosceles triangle has two equal sides.
- A scalene triangle has three different side lengths.
Classification by angles
- An acute triangle has three angles smaller than 90°.
- A right triangle has one angle equal to 90°.
- An obtuse triangle has one angle greater than 90°.
The angles of every triangle add to 180°. A triangle cannot contain two right angles or two obtuse angles because those angles alone would total at least 180°.
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