Discussion :: Probability
- A box contains 3 white, 4 red and 7 blue erasers. If five erasers are taken at random then the probability that all the five are blue color is: -
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Answer : Option B
Explanation :
Total number of erasers in the box = 3 + 4 + 7 = 14.
Let S be the sample space.
Then, n(S) = number of ways of taking 5 out of 14.
Therefore, n(S) = 14C5 = (14 x 13 x 12 x 11 x 10)/(2 x 3 x 4 x 5) = 14 x 13 x 11 = 2002
Let E be the event of getting all the 5 blue erasers.
Therefore, n(E) = 7C5 = (7 x 6 x 5 x 4 x 3)/(2 x 3 x 4 x 5) = 21.
Now, the required probability = n(E)/n(S) = 21/2002 = 3/286.
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