Class 9 Maths – Lines and Angles MCQ

1. If two parallel lines are intersected by a transversal, then the alternate interior angles are:

a) Complementary
b) Supplementary
c) Equal
d) Unequal

Answer:

c) Equal

Explanation:

For two parallel lines cut by a transversal, the alternate interior angles are congruent or equal.

2. An angle that measures exactly 180 degrees is called:

a) Acute angle
b) Right angle
c) Straight angle
d) Reflex angle

Answer:

c) Straight angle

Explanation:

A straight angle lies on a straight line and measures 180 degrees.

3. Vertically opposite angles are always:

a) Acute
b) Supplementary
c) Equal
d) Obtuse

Answer:

c) Equal

Explanation:

When two lines intersect, the angles formed opposite to each other are called vertically opposite angles, and they are always equal.

4. The sum of angles around a point is:

a) 90 degrees
b) 180 degrees
c) 270 degrees
d) 360 degrees

Answer:

d) 360 degrees

Explanation:

The total of all angles around a point is 360 degrees.

5. If two lines are perpendicular to each other, then the angle between them is:

a) 0 degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees

Answer:

c) 90 degrees

Explanation:

Two lines are said to be perpendicular if they intersect to form a right angle, which measures 90 degrees.

6. Which of the following angles is the smallest?

a) Acute angle
b) Right angle
c) Obtuse angle
d) Reflex angle

Answer:

a) Acute angle

Explanation:

An acute angle measures less than 90 degrees, making it the smallest among the given options.

7. An angle measuring more than 90 degrees but less than 180 degrees is termed as:

a) Acute angle
b) Right angle
c) Obtuse angle
d) Reflex angle

Answer:

c) Obtuse angle

Explanation:

An obtuse angle is greater than 90 degrees but less than 180 degrees.

8. If a ray stands on a line, then the sum of the two adjacent angles so formed is:

a) 45 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer:

c) 180 degrees

Explanation:

When a ray stands on a line, it divides the line into two adjacent angles that are supplementary, meaning their sum is 180 degrees.

9. Two lines in a plane that never meet, irrespective of how long they are extended, are called:

a) Intersecting lines
b) Perpendicular lines
c) Parallel lines
d) Secant lines

Answer:

c) Parallel lines

Explanation:

Parallel lines are two or more lines that run in the same direction and never meet, no matter how far they are extended.

10. Which of the following pairs of angles are always supplementary?

a) Linear pair
b) Vertically opposite angles
c) Corresponding angles
d) Alternate interior angles

Answer:

a) Linear pair

Explanation:

A linear pair is a pair of adjacent angles whose non-common sides are opposite rays. They always sum up to 180 degrees, making them supplementary.

11. The sum of all interior angles of a triangle is:

a) 90 degrees
b) 180 degrees
c) 270 degrees
d) 360 degrees

Answer:

b) 180 degrees

Explanation:

The total of all interior angles in any triangle is always 180 degrees.

12. If two lines are cut by a transversal such that a pair of alternate exterior angles are equal, then the lines are:

a) Intersecting
b) Not parallel
c) Parallel
d) Perpendicular

Answer:

c) Parallel

Explanation:

Equal alternate exterior angles are a condition for two lines to be parallel when cut by a transversal.

13. Which of the following statements is always true?

a) Adjacent angles are supplementary.
b) All right angles are equal.
c) Obtuse angles are complementary.
d) Acute angles are supplementary.

Answer:

b) All right angles are equal.

Explanation:

A right angle always measures 90 degrees, so all right angles are equal.

14. The angles that have a common vertex and a common side but no common interior points are called:

a) Supplementary angles
b) Vertically opposite angles
c) Adjacent angles
d) Complementary angles

Answer:

c) Adjacent angles

Explanation:

Adjacent angles share a common vertex and side but don't have any interior points in common.

15. When two lines intersect, the angles formed opposite to each other are called:

a) Complementary angles
b) Adjacent angles
c) Vertically opposite angles
d) Supplementary angles

Answer:

c) Vertically opposite angles

Explanation:

When two lines intersect, they form pairs of equal angles opposite to each other, called vertically opposite angles.

16. The angles which sum up to 90 degrees are:

a) Linear
b) Complementary
c) Supplementary
d) Adjacent

Answer:

b) Complementary

Explanation:

Two angles are complementary if the sum of their measures is 90 degrees.

17. Two lines that intersect to form right angles are:

a) Parallel lines
b) Adjacent lines
c) Perpendicular lines
d) Intersecting lines

Answer:

c) Perpendicular lines

Explanation:

Two lines that intersect to form right angles (90 degrees) are perpendicular to each other.

18. The angle which is equal to its complementary angle is:

a) 30 degrees
b) 45 degrees
c) 60 degrees
d) 90 degrees

Answer:

b) 45 degrees

Explanation:

If an angle and its complementary angle are equal, then each angle is 45 degrees because their sum is 90 degrees.

19. If one of the angles in a linear pair is acute, then the other angle is:

a) Acute
b) Right
c) Obtuse
d) Straight

Answer:

c) Obtuse

Explanation:

In a linear pair, if one angle is acute (less than 90 degrees), then the other must be obtuse because their sum is 180 degrees.

20. An angle whose measure is greater than 180 degrees but less than 360 degrees is:

a) Acute angle
b) Right angle
c) Obtuse angle
d) Reflex angle

Answer:

d) Reflex angle

Explanation:

A reflex angle measures more than 180 degrees but less than 360 degrees.

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