Question

A person writes 4 letters and addresses on 4 envelopes. If the letters are placed in the envelopes at random, the probability that not all letters are placed in correct envelopes is

Solution

Correct option is

23/24

Required probability

                                          = 1 – P (all the letters are put is correct envelops)

The numbers of ways of putting the letters in the envelops   

                                                          

The number of ways of putting letters in correct envelops = 1

SIMILAR QUESTIONS

Q1

A pair of unbiased dice is rolled together till a sum of either 5 or 7 is obtained. The probability that 5 comes before 7 is

Q2

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Q3

The probability that a student is not a swimmer is 1/5. The probability that out of 5 students exactly 4 is swimmer is

Q4

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Q5

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Q6

A natural number x is chosen at random from the first one hundred natural numbers. The probability that   is

Q7

An experiment has 10 equally likely outcomes. Let A and B two non – empty events of the experiment. If a consists of 4 outcomes, the number of outcomes that B must have so that A and B are independent, is

Q8

If AB and C are the events such that P(B) = 3/4, P(A ∩ B ∩ C’) = 1/3P(A’ ∩ B ∩ C’) = 1/3, then P (B ∩ C) is equal to

Q9

A fair coin is tossed n times. If the probability that head occurs 6 times is equal to the probability that occurs 8 times, then value of n is

Q10

A letter is known to have come from either TATANAGAR or CALCUTTA. On the envelope, just two consecutive letters, TA, are visible. The probability that the letter has come from CACUTTA is