Classifying triangles

Identify equilateral, isosceles, scalene and right-angled triangles

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1
A triangle with three equal sides is called a ___ triangle. A) scalene B) isosceles C) equilateral D) right-angled
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2
A triangle with exactly two equal sides is called ___. Two equal sides = ___ triangle
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3
Is this statement true or false? A scalene triangle has no equal sides. A) True B) False
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4
What is the angle in each corner of an equilateral triangle? A) 45° B) 60° C) 90° D) 120°
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5
Match each triangle to its description. Match each item on the left to one on the right. Left: Equilateral, Isosceles, Scalene, Right-angled Right: 3 equal sides, 2 equal sides, No equal sides, One 90° angle
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6
A right-angled triangle has angles 90°, 50° and ___. A) 30° B) 40° C) 45° D) 50°
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7
Is this statement true or false? An isosceles triangle has two equal angles. A) True B) False
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8
A triangle has sides 5 cm, 5 cm and 8 cm. What type of triangle is it? A) Equilateral B) Isosceles C) Scalene D) Right-angled
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9
A triangle has angles 90°, 45° and 45°. What two type names describe it? Right-angled and ___ triangle
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10
Is this statement true or false? A triangle can have two 90° angles. A) True B) False
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Answer key

Classifying triangles · for parents and teachers

1
equilateral
An equilateral triangle has three equal sides and three 60° angles.
2
isosceles
An isosceles triangle has two equal sides and two equal base angles.
3
True
A scalene triangle has all three sides of different lengths.
4
60°
An equilateral triangle has three equal angles, each 180° ÷ 3 = 60°.
5
Equilateral → 3 equal sides; Isosceles → 2 equal sides; Scalene → No equal sides; Right-angled → One 90° angle
Equilateral: 3 equal sides. Isosceles: 2 equal sides. Scalene: 0 equal sides. Right-angled: one 90° angle.
6
40°
180° - 90° - 50° = 40°.
7
True
An isosceles triangle has two equal sides and two equal angles opposite them.
8
Isosceles
Two sides are equal (5 cm and 5 cm), so it is isosceles.
9
isosceles
Two equal angles means two equal sides, so it is right-angled isosceles.
10
False
Two 90° angles would already total 180°, leaving nothing for the third angle. So a triangle cannot have two right angles.