There are 15 points in a plane, no two of which are in a straight line except 4, all of which are in a straight line. The number of triangles that can be formed by using these 15 points is ___.
A. 404
B. 415
C. 451
D. 490
Answer:C
There are 15 points in a plane, no two of which are in a straight line except 4, all of which are in a straight line. The number of triangles that can be formed by using these 15 points is ___.
A. 404 B. 415 C. 451 D. 490