5 different -letters are kept into 5 envelopes with different address unmindfully. Find the: probability that two letters have been kept into the envelopes of their proper address

There are four letters and four envelops with proper address. Find the probability that the letters are not in proper envelops.

There are n letters and n addressed envelopes. Find the probability that all the letters are not kept in the right envelope.

Five different letters are put at random inside five addressed envelopes. Find the probability of putting exactly 2 letters in the correct envelopes.

There are four letters and four envelopes bearing addresses at random. The probability that the letters are placed in correct envelopes is (K)/(24) , then find the value of K.

Find the probability of getting total of 5 or 6 in a single throw of two dice.

12 balls are kept in 3 different boxes, then the probability that the box will contain 3 balls is -

Five different marbles are placed in 5 different boxes randomly. Then the probability that exactly two boxes remain empty is (each box can hold any number of marbles) 2//5 b. 12//25 c. 3//5 d. none of these

5% of the electric valves are defective. 10 valves are drawn at random. Find the probability that at least two defective valves are found.

5% of the electric values are defective. 10 values are drawn at random. Find the probability that at least two defective values are found.

Three letters are dictated to three person and an envolopes at random so that each envelope contains exactly one letter. Find the probability that at least one letter is in its proper envelope.