A department organizes Party A and Party B to decipher a password, and whether each of them can decipher the password is independent of each other. It is known that the probabilities of Party A and Party B deciphering the password independently are 13 and 14 respectively. (1) find out the probability of one of them deciphering the password; (2) find out the probability of them deciphering the password; (3) now transfer Party B away, and Party A stays, and the probability of deciphering the password is not low At 80%, how many people should be added at least?

A department organizes Party A and Party B to decipher a password, and whether each of them can decipher the password is independent of each other. It is known that the probabilities of Party A and Party B deciphering the password independently are 13 and 14 respectively. (1) find out the probability of one of them deciphering the password; (2) find out the probability of them deciphering the password; (3) now transfer Party B away, and Party A stays, and the probability of deciphering the password is not low At 80%, how many people should be added at least?


If a and B decode the code respectively as events a and B, then p (a) = 13, P (b) = 14. (1) one of a and B decodes the code, including two cases: a decodes but B does not decode and B decodes but a does not decode, then p (AB + AB) = P (a) P (b) + P (a) P (b) = 23 × 14 + 13