Question 39
Back to Exercise
Three points are marked on each side of a triangle, as shown (the corners are not among the marked points).
How many different straight lines pass through at least two of the nine marked points?
- A 30 Correct
- B 36
- C 27
- D 33
Correct Answer: Option A
All pairs: 9C2 = 36
Pairs on the same side: 3 × 3C2 = 9, but they give only 3 lines
36 − 9 + 3 = 30
Trap: 27 forgets to add back the 3 side lines.
Answer: 30
Discussion & Comments 0
Share your method, a shortcut, or ask about a step you didn't follow.
No comments yet. Be the first to share your solution!