If 20 points are marked on a circle, how many chords can be drawn… - Vidyadip

Question

If 20 points are marked on a circle, how many chords can be drawn?

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Answer

To draw a chord we need to join two points on the circle.
There are $20$ points on a circle.
$\threfore$ Total number of chords possible from these points
$={ }^{20} C _2$
$=\frac{20 !}{2 ! 18 !}$
$=\frac{20 \times 19 \times 18 !}{2 \times 1 \times 18 !}$
$=190$

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