Classify the angle as acute, right, obtuse, straight:

Question

Classify the angle as acute, right, obtuse, straight:

List I — (a), (b), (c), (d) (figures as printed in the booklet)

List II — (i) Acute (ii) Right (iii) Straight (iv) Obtuse

Match I with II.

1. A. a-ii, b-iv, c-i, d-iii
2. B. a-ii, b-iv, c-iii, d-i
3. C. a-ii, b-i, c-iv, d-iii (Correct answer)
4. D. a-ii, b-i, c-iii, d-iv

Correct Answer

Option C — a-ii, b-i, c-iv, d-iii

Detailed Solution & Explanation

The correct answer is a-ii, b-i, c-iv, d-iii.

Key Points

• Reading the four figures in List I against the angle types in List II:
  • (a) — Right angle (ii): the two rays meet at exactly 90°, marked in the figure by the small square at the vertex.
  • (b) — Acute angle (i): the rays form a narrow opening of less than 90°.
  • (c) — Obtuse angle (iv): the opening is wide, more than 90° but less than 180°.
  • (d) — Straight angle (iii): the two rays point in exactly opposite directions along one line, giving 180°.
• The correct pairing is therefore a-ii, b-i, c-iv, d-iii.

Additional Information

• The full classification by magnitude: acute (< 90°), right (= 90°), obtuse (90°-180°), straight (= 180°), reflex (180°-360°) and complete (= 360°).
• The small square symbol at a vertex is the standard notation for a right angle and is usually the fastest way to identify figure (a) in questions of this type.
• Two angles summing to 90° are complementary; two summing to 180° are supplementary.