Combinations question (1 Viewer)

[clintmyster]

There are ten points in a plane, five of which are collinear. No other set of three of these points is collinear. How many triangles can be formed using the ten points as vertices.

 

[midifile]

There are ten points in a plane, five of which are collinear. No other set of three of these points is collinear. How many triangles can be formed using the ten points as vertices.

Number of triangles = all possible triangles - impossible triangles
=¹⁰C₃ - ⁵C_{3
= 110}

 

[clintmyster]

thanks!