SOLUTION: how many quadrilateral can be formed from 25 points out of which 7 are collinear

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Question 936407: how many quadrilateral can be formed from 25 points out of which 7 are collinear
Answer by srinivas.g(540) About Me  (Show Source):
You can put this solution on YOUR website!
4 points are needed to form a quadrilateral
we need to select 4 points out of 25 points
so no of quadrilaterals that can be formed out of 25 points = 25c4
=%2825%2A24%2A23%2A22%29%2F%284%2A3%2A2%2A1%29
=25*23*22
=12650
but out of 25 points , 7 points are collinear( which lies on same line)
so they form a line . they cannot form quadrilaterals
so no of quadrilaterals that cannot be formed due to collinear points = 7c4
=%287%2A6%2A5%2A4%29%2F%284%2A3%2A2%2A1%29
=7%2A5
=35
no of quadrilateral can be formed from 25 points out of which 7 are collinear are = 12650-35
=12615
Result : 12615