JEE Main & Advanced
Mathematics
Permutations and Combinations
Question Bank
Geometrical Problems
question_answer
The number of triangles that can be formed by choosing the vertices from a set of 12 points, seven of which lie on the same straight line, is [Roorkee 1989; BIT 1989; MP PET 1995;Pb. CET 1997, 98; Roorkee 2000; DCE 2002; AMU 2005]
A)185
B)175
C)115
D)105
Correct Answer:
A
Solution :
Required number of ways \[={{\,}^{12}}{{C}_{3}}{{-}^{7}}{{C}_{3}}\] \[=220-35=185\].