Permutations And Combinations Question 79

Question: The number of straight lines that can be formed by joining 20 points no three of which are in the same straight line except 4 of them which are in the same line [Kerala (Engg.) 2002]

Options:

A) 183

B) 186

C) 197

D) 185

Show Answer

Answer:

Correct Answer: D

Solution:

  • Required number $ ={{}^{20}}C_2-{{}^{4}}C_2+1 $ $ =\frac{20\times 19}{2}-\frac{4\times 3}{2}+1=190-6+1=185. $

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