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A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?

Options:
A .  \(\frac{10}{21}\)
B .  \(\frac{11}{21}\)
C .  \(\frac{2}{7}\)
D .  \(\frac{5}{7}\)
Answer: Option A

Total number of balls = (2 + 3 + 2) = 7.


Let S be the sample space


Then, n(S)  = Number of ways of drawing 2 balls out of 7


7C2 


= \(\frac{(7\times6)}{(2\times1)}\)


=21.


Let E = Event of drawing 2 balls, none of which is blue.


So, n(E) = = Number of ways of drawing 2 balls out of (2 + 3) balls.


5C2


= \(\frac{(5\times4)}{(2\times1)}\)


=10.


So, \(P(E) = \frac{n(E)}{n(S)}=\frac{10}{21}\)


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