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Question
If 20 points are marked on a circle, how many chords can be drawn?
Solution
To draw a chord we need to join two points on the circle.
There are 20 points on the circle.
∴ We can draw 20C2 chords of the circle.
= `(20!)/((20 - 2)!2!)`
= `(20!)/(18!2!)`
= `(20 xx 19xx18!)/(2xx1xx18!)`
= 190
190 chords can be drawn.
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