Get a key joke

The first one tried 3 times, the second one tried 2 times, and the last one must be the last lock, but it must be opened according to the meaning of the question, so the last one should be tried once, a total of 5 times!

It is wrong to say at least three times, because the topic is "How many times can I be insured?" Pay attention to this guarantee! If it is only three times, it may be opened, but there is no guarantee that it will be opened. If guaranteed, at least five times!

Extended data

Basic counting principle and application of two commonly used arrays

1, addition principle sum classification counting method;

Each method in each class can accomplish this task independently; The specific methods of the two different methods are different (that is, the classification is not heavy); Any way to accomplish this task falls into one category or another.

2. Multiplication principle and step counting method:

This task cannot be accomplished by any method or step. It must be completed in a sequence of n steps to complete the task. The calculation of each step is independent of each other. As long as the methods used in one step are different, the corresponding methods will be different.