Q. 134.4( 5 Votes )

# How many chords can be drawn through 21 points on a circle?

Answer :

Number of points=21

⇒n=21

A chord connects circle at two points.

⇒r=2

⇒Number of chords from 21 points= ^{n}C_{r}

⇒ ^{n}C_{r}= ^{21}C_{2}

⇒^{21}C_{2}=

⇒^{21}C_{2}=

⇒^{21}C_{2}=

⇒^{21}C_{2}=

⇒^{21}C_{2}=210 chords.

Ans: 210 chords can be drawn through 21 points on a circle.

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