Class 9 Maths MCQs – Angle Sum Property & Exterior Angle Theorem
Class 9 Maths MCQs – Angle Sum Property & Exterior Angle Theorem
Class: 9 | Subject: Mathematics | Chapter: 7 – Triangles
Board: CBSE | Based on Latest NCERT Curriculum
Board: CBSE | Based on Latest NCERT Curriculum
These MCQs are strictly based on the CBSE Class 9 Mathematics syllabus and NCERT textbook guidelines. Ideal for school exams and board preparation.
1. The sum of interior angles of a triangle is:
Answer: B. 180°
According to the Angle Sum Property, the sum of three interior angles of any triangle is 180°.
According to the Angle Sum Property, the sum of three interior angles of any triangle is 180°.
2. If two angles of a triangle are 50° and 60°, the third angle is:
Answer: A.
180 − (50 + 60) = 70°.
180 − (50 + 60) = 70°.
3. An exterior angle of a triangle equals:
Answer: B.
Exterior Angle Theorem states it equals sum of two remote interior angles.
Exterior Angle Theorem states it equals sum of two remote interior angles.
4. If one exterior angle is 110° and one interior opposite angle is 40°, the other interior opposite angle is:
Answer: A.
110 − 40 = 70°.
110 − 40 = 70°.
5. If all angles of a triangle are equal, each angle measures:
Answer: B.
Equilateral triangle → 180 ÷ 3 = 60°.
Equilateral triangle → 180 ÷ 3 = 60°.
6. In a right triangle, if one acute angle is 35°, the other is:
Answer: B.
90 − 35 = 55°.
90 − 35 = 55°.
7. If one angle of triangle is 90°, sum of other two is:
Answer: B.
180 − 90 = 90°.
180 − 90 = 90°.
8. An exterior angle is always:
Answer: C.
Exterior angle equals sum of two remote interior angles.
Exterior angle equals sum of two remote interior angles.
9. If exterior angle is 120°, sum of two interior opposite angles is:
Answer: B.
Exterior angle equals sum of remote interior angles.
Exterior angle equals sum of remote interior angles.
10. The smallest angle in triangle is opposite to:
Answer: B.
Angle opposite smaller side is smaller.
Angle opposite smaller side is smaller.
11. Largest angle is opposite to:
Answer: C.
Angle-side opposite relationship.
Angle-side opposite relationship.
12. If two angles are 30° and 80°, third is:
Answer: A.
180 − 110 = 70°.
180 − 110 = 70°.
13. Exterior angle equals sum of:
Answer: B.
Exterior angle theorem.
Exterior angle theorem.
14. Sum of exterior angles of triangle (one at each vertex) is:
Answer: B.
Total turn around figure equals 360°.
Total turn around figure equals 360°.
15. If one angle is obtuse, triangle is:
Answer: C.
Triangle with one obtuse angle is obtuse triangle.
Triangle with one obtuse angle is obtuse triangle.
16. In equilateral triangle, exterior angle is:
Answer: B.
180 − 60 = 120°.
180 − 60 = 120°.
17. If triangle has angles 40°, 60°, and 80°, it is:
Answer: A.
All angles less than 90°.
All angles less than 90°.
18. Exterior angle is supplementary to:
Answer: B.
Exterior angle forms linear pair with adjacent interior angle.
Exterior angle forms linear pair with adjacent interior angle.
19. If two angles are equal in triangle, triangle is:
Answer: C.
Equal angles → opposite sides equal.
Equal angles → opposite sides equal.
20. Angle sum property applies to:
Answer: A.
Sum of interior angles of triangle is always 180°.
Sum of interior angles of triangle is always 180°.