Question

There are 25 points on a plane of which 7 are collinear. how many quadrilaterals can be formed ?

Answer 1

To form a quad. 4 points are needed
no of ways of selecting 4 points from 25 points. is 25c4 (combination)
but 7 are collinear therfore 25C4 - 7C4=12615

Answer 2

Answer: There are 11895 quadrilaterals that can be formed.

Step-by-step explanation:

Since we have given that

Number of points = 25

Number of collinear = 7

We need to find the number of quadrilaterals.

Number of non collinear points = 25-7=18

So, Number of quadrilaterals that can be formed is given by

$^{18}C_4+^{18}C_3\times ^7C_1+^{18}C_2\times ^7C_2\\\\=3060+5712+3123\\\\=11895$

Hence, there are 11895 quadrilaterals that can be formed.