The probability of losing a letter at the post office is 0.03, and a telegram is 0.01.

The probability of losing a letter at the post office is 0.03, and a telegram is 0.01. Two letters and one telegram sent. What is the probability that a) only a telegram will arrive b) at least one of the items?

a) If only a telegram reached, then two letters were lost, this probability is P = 0.03 * 0.03 * 0.99 = 0.000891;

b) To find the probability that at least one of the items arrived, you need to subtract the probability from 1 when the events, when all three were lost, this probability is equal to P = 1- (0.03 * 0.01 * 0.03) = 1-0.000009 = 0.999991.