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Ex 7.4, 3 - How many chords can be drawn through 21 points - Ex 7.4

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Ex7.4, 3 How many chords can be drawn through 21 points on a circle? Number of points = 21 Hence n = 21 A chord connects circle at 2 points Hence, r = 2 Number of chord from 21 points = nCr = 21C2 = 21!/2!(21−2) = 21!/(2! 19! ) = (21 × 20 × 19!)/((2 × 1) × 19!) = (21 × 20)/(2 ) = 210 chords.

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.