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Difficulty: 2/102023 NMTC 2023 (QII-30)

Maximum number of intersection points of 5 non parallel distinct lines in plane are ________.

Guide / Hint

Hint 1: The maximum number of intersections occurs when every pair of lines intersects at a unique point.

Hint 2: This is equivalent to choosing 2 lines out of 5: .

Hint 3: Compute the value of .

Solution

Step 1 (Maximum Intersections Condition): The maximum number of intersection points of distinct lines in a plane occurs when:

  1. No two lines are parallel (every pair of lines intersects at exactly one point).

  2. No three lines are concurrent (no point is shared by three or more lines).

Step 2 (Apply Combinations): Under these conditions, every choice of 2 lines out of distinct lines yields exactly 1 unique intersection point. Therefore, the maximum number of intersection points for lines is:

Step 3 (Substitute n = 5):

Step 4 (Conclusion): The maximum number of intersection points is exactly 10.

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