Question

How many triangles can be formed by joining 12 points, 7 of which are collinear?

Answer 1

Answer:

185

Step-by-step explanation:

# triangles

= ( # ways choosing 3 points from the 12 )  -  ( # ways of choosing 3 points from the 7, since these choices don't make triangles after all)

= $\binom{12}{3} - \binom{7}{3}$

= 220 - 35

= 185

Answer 2

Answer:

answer= 185

Step-by-step explanation:

let triangle formed by joining 12 point be p

let the triangle formed by joining 7 collinear points q

p-q=no. of triangle formed

220-35=185