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Mathematics

State which of the following statements are true and which are false:

(i) A triangle can have two right angles.

(ii) A triangle cannot have more than one obtuse angle.

(iii) A triangle has at least two acute angles.

(iv) If all the three sides of a triangle are equal, it is called a scalene triangle.

(v) A triangle has four sides.

(vi) An isosceles triangle is an equilateral triangle also.

(vii) An equilateral triangle is an isosceles triangle also.

(viii) A scalene triangle has all its angles equal.

Triangles

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Answer

(i) False
Reason — The sum of angles of a triangle is 180°. If a triangle had two right angles, their sum alone would be 180°, leaving 0° for the third angle, which is not possible.

(ii) True
Reason — If a triangle had two obtuse angles (each greater than 90°), their sum alone would exceed 180°, which violates the angle sum property.

(iii) True
Reason — Since the sum of angles of a triangle is 180°, a triangle can have at most one angle that is right or obtuse. So at least two angles must be acute.

(iv) False
Reason — If all three sides of a triangle are equal, it is called an equilateral triangle, not a scalene triangle.

(v) False
Reason — A triangle has three sides, not four.

(vi) False
Reason — An isosceles triangle has only two sides equal, so it is not necessarily an equilateral triangle (which has all three sides equal).

(vii) True
Reason — An equilateral triangle has all three sides equal, which means it has at least two equal sides. So it is also an isosceles triangle.

(viii) False
Reason — A scalene triangle has all sides of different lengths, so all its angles are also different (not equal).

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