Work through the levels in order. Type your answer and press Check — open the worked solution if you get stuck. Answers like -6, 3/4 or 0.25 are typed exactly as shown.
Level 1 · Warm-up
1 A triangle has three equal sides. Name it by its sides.
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Three equal sides means it is equilateral.
2 A triangle has no equal sides at all. Name it by its sides.
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No equal sides means it is scalene.
3 A triangle has one angle of exactly 90°. Name it by its angles.
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A 90° angle is a right angle, so the triangle is right-angled.
Level 2 · Core
4 A triangle has angles 70°, 60° and 50°. Name it by its angles.
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The largest angle is 70°, which is under 90°, so every angle is acute and the triangle is acute.
5 A triangle has angles 110°, 40° and 30°. Name it by its angles.
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The largest angle, 110°, is over 90°, so the triangle is obtuse.
6 A triangle has two sides of 6 cm and one side of 4 cm. Name it by its sides.
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Exactly two sides are equal, so the triangle is isosceles.
Level 3 · Challenge
7 A triangle has angles 90°, 45° and 45°. Give BOTH of its names, one from each list.
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The 90° angle makes it right-angled, and the two equal angles mean two equal sides, so it is right-angled and isosceles.
8 Every angle of a certain triangle measures 60°. Name it by its sides.
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Three equal angles mean three equal sides, so the triangle is equilateral.
9 Can a triangle be both equilateral and right-angled? Answer yes or no.
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No. Every angle of an equilateral triangle is 60°, so none of them can be 90°.