Q.3.     How many chords can be drawn through 21 points on a circle?

Answers (1)
S seema garhwal

To draw chords 2 points are required on the circle.

To know the number of chords on the circle , when points on the circle are 21.

Combinations =Number of chords  =^{21}C_2

                                                          =\frac{21!}{(21-2)!2!}

                                                          =\frac{21!}{19!2!}

                                                          =\frac{21\times 20}{2}

                                                             =210

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