Question

How many triangles are formed by selecting points from a set of 15 points out of which 8 are collinear?

(a) 800   (b) 824    (c) 844     (d) 854

Comments

399..correct

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3 points from nonlinear group=7C3=35

2 points from nonlinear group and 1 point from collinear =(7C2)*(8c1) =168

2 points from collinear group and 1 from 7 points =(8C2)*(7C1)=196

35+168+196=399

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yes I did same