Important Questions: Lines and Angles - Class 7 MCQ

• When the sum of the measures of two angles is 90°, these angles are called complementary angles.
• Complementary angles can be adjacent or non-adjacent, but their sum is always 90°.
• Supplementary angles sum up to 180°, not 90°.
• Adjacent angles share a common side and vertex but aren't defined by their sum.
• Vertically opposite angles are formed by intersecting lines and are equal, not defined by a specific sum.

• Complementary angles are defined as two angles whose measures add up to 90°.
• This means if you have two angles, and their total is 90°, they are complementary.
• For example, if one angle is 30°, the other must be 60° to be complementary.
• Therefore, the sum of complementary angles is always 90°.
• Thus, the correct answer is D: 90°.

90° – 30° = 60°.

60°+ 30° = 90°.

180° – 120° = 60°.

120° + 90° = 210° ≠ 180°.

• Linear Pair Definition: A linear pair consists of two adjacent angles whose non-common sides form a straight line.
• Supplementary Angles: Angles that add up to 180 degrees are called supplementary angles.
• Relation to Linear Pair: Since the non-common sides of a linear pair form a straight line, the angles together measure 180 degrees, making them supplementary.

Thus, the angles in a linear pair are supplementary.

120° + 60° = 180°.

• A linear pair consists of two adjacent angles whose non-common sides form a straight line.
• A straight line measures 180°.
• Therefore, the sum of the measures of the angles in a linear pair is 180°.
• This is because the angles add up to form a straight line, which is always 180°.
• Thus, the correct answer is B: 180°.

• Vertically opposite angles are formed when two lines intersect.
• These angles are always equal to each other.
• Options A, B, and C are true because vertically opposite angles can be both acute, obtuse, or right angles, as long as they are equal.
• Option D is false because vertically opposite angles are always equal.
• Therefore, statement D is incorrect.

∠x – ∠y = (180° – 62°) – 62° = 118° – 62° = 56°.

∠2 = ∠6, corresponding angles.

∠1, ∠2 simply make a linear pair.

x° = 2(90° – x°) ⇒ x° = 60°.

∠1 = ∠2; ∠1 + ∠2 = 100°
∴ ∠1 = 50°
∴ ∠4 = 180° – 50° = 130°.