A box contains 3 white 4 red and 7 blue erasers If five erasers are taken at random then the probabi...........

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.

Hence, option 3 is the correct answer.