A complete graph has 21 line segments (every pair of points joined). How many points does it have?
- A.6
- B.7 ✓
- C.8
- D.9
Explanation: If there are n points, the number of segments is n(n-1)/2. For n=7: 7×6/2 = 21.
Class 6 IMO Mathematics Olympiad practice · Algebraic Thinking · Patterns in Mathematics
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