Q. 45.0( 2 Votes )

Out of 18 points in a plane, no three are in the same line except five points which are collinear. Find the number of lines that can be formed joining the point.

[Hint: Number of straight lines =18C25C2 + 1]

Answer :

Formula:- (i)nCr


Given:-


Number of points =18


Number of Collinear points =5


Number of lines form by 18 points =18C2


For 5 points are collinear=5C2


the number of lines that can be formed joining the point.


=18C2-5C2+1



=153-10+1


=144


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