2018 · Q87
If two lines AB and CD intersect at O such that ∠ AOC = 5 ∠ AOD, then the four angles at O are
Elementary MathematicsGeometry: Lines, Angles and Triangles
- A40°, 40°, 140°, 140°
- B30°, 30°, 150°, 150°
- C30°, 45°, 75°, 210°
- D60°, 60°, 120°, 120°
Explanation
Angles AOC and AOD form a linear pair: angle AOC + angle AOD = 180 degrees. With angle AOC = 5 angle AOD, we get 6 angle AOD = 180, so angle AOD = 30 degrees and angle AOC = 150 degrees. The four angles are 30, 150, 30, 150 degrees. Hence option B.