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प्रश्न
Ten points are plotted on a plane. Find the number of straight lines obtained by joining these points if no three points are collinear
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उत्तर
A line is drawn by joining 2 points from the given 10 points.
∴ number of straight lines
= 10C2
= `(10!)/(2!8!)`
= `(10 xx 9 xx 8!)/(2 xx 8!)`
= 45, if no three points are collinear.
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