Arithmetic Ability
 Probability

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Q.

The first 8 alphabets are written down at random. what is the probability that the letters b,c,d,e always come together ?

View Answer

Correct choice: D

Explanation:

The 8 letters can be written in 8! ways. n(S) = 8! Let E be the event that the letters b,c,d,e always come together when the first 8 alphabets are written down. Now the letters a, (bcde), f, g and h can be arranged in 5! ways. The letters b,c,d and e can be arranged themselves in 4! ways. n(E) = 5! x 4! Now, the required P(E) = n(E)/n(S) = 5! x 4!/8! = 1/14 Hence the answer is 1/14.
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