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Problem 25

Combinatorics Difficulty 1.0 Find the answer CEMC Gauss (Grade 7) · Canada · 1998

Ten points are spaced equally around a circle. How many different chords can be formed by joining any 2 of these points? (A chord is a straight line joining two points on the circumference of a circle.)

(A) $9$ (B) $45$ (C) $17$ (D) $66$ (E) $55$

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