Statistics And Probability Question 228

Question: Three of the six vertices of a regular hexagon are chosen at random. The probability that the triangle with these three vertices is equilateral, is equal to

[IIT 1995; MP PET 2002, 04]

Options:

A) $ \frac{1}{2} $

B) $ \frac{1}{5} $

C) $ \frac{1}{10} $

D) $ \frac{1}{20} $

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Answer:

Correct Answer: C

Solution:

  •                 Total number of triangles which can be formed is equal to  $ {}^{6}C_3=\frac{6\times 5\times 4}{1\times 2\times 3}=20 $                     Number of equilateral triangles = 2                     
    

$ \therefore $ Required probability $ =\frac{2}{20}=\frac{1}{10}. $