A letter lock contains 4 rings, each ring containing 5 letters. All possible trails are made to open the lock and the lock opens in only one way. The probability for the lock to open is

A number lock contains 4 rings each ring containing 6 numbers . All the possible attempts of opening the lock are made but the lock opens in only one way. The probability for the lock to open is

a Letter lock contains 5 rings each marked with four different letters . The number of all possible iunsuccesful attempts to open the lock is

A letter lock has 3 rings and each ring has 5 letters. Determine the maximum number of trails that may be required to open the lock.

A letter lock consists of three rings each marked with 5 different letters. Number of maximum attempts to open the lock is

A letter lock has 3 rings each containing 6 different letters. What is the maximum number of false trials that can be made before the lock is opened?

A letter lock consists of three rings each marked with 10 different letters. No. of ways to make an unsuccessful attempts to open the lock is

To open a lock, a key is taken out from a collection of n keys at random. If the lock is not opend with this key, it is put back into the collection and another key is tried. The process is repeated again and again. If it is given that with only one key in the collection, the lock can be opend, then the probability that the lock will open in n trials, is