Question

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

Answer 1

collinear points cannot form a triangle so,=25-7=18
now, 18 points are non collinear=18
3 points needed to form 1 triangle so,
18÷3= 6 triangles can be formed...

Answer 2

Answer: There are 2265 triangles that can be formed.

Step-by-step explanation:

Since we have given that

Number of points on a plane = 25

Number of collinear = 7

Number of non collinear points = 25-7 =18

We need to find the number of triangles that can be formed.

So, the number of triangles would be

$^{18}C_3+^{18}C_2\times ^7C_1+^{18}C_1\times ^7C_2\\\\=816+1071+378\\\\=2265$

Hence, there are 2265 triangles that can be formed.