Question 17
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12 points lie in a plane; exactly 5 of them are on one line and no other three are collinear. How many different straight lines do they determine?
- A 57 Correct
- B 66
- C 56
- D 46
Correct Answer: Option A
All pairs = 66
The 5 collinear points give 5C2 = 10 pairs but only 1 line
66 − 10 + 1 = 57
Trap: 56 forgets to add back that one line.
Answer: 57
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