Lessons

General Aptitude
34.1 Probability - General Questions

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Q.

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?

View Answer

Correct choice: A

Explanation:

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 `
 
= (7 x 6)/
(2 x 1)
  = 21.

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

n(E) = Number of ways of drawing 2 balls out of (2 + 3) balls.
  = 5C2
 
= (5 x 4)/
(2 x 1)
  = 10.
∴ P(E) = n(E)/ = 10/ .
n(S) 21
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