91影视

The code for opening a lock comprises three digits to be chosen from 0 to 49.

The order of the digits is important for opening the lock.

Combination: Count the ways to select a specific number of items from a list without replacement inwithout any particular order.

Permutation: Count the ways to select a specific number of items from a list without replacement inwhere orders matter.

It is given that the code for opening the lock needs three digits to be chosen from 0 to 49.

The arrangement of the digits matters in opening the lock.

The following two cases can appear:

• The digits may repeat (selected with replacement): In this case, neither combination nor permutation can be used. Thus, the name combination lock is inappropriate.
• The digits cannot repeat (selected without replacement): In this case, either combination or permutation can be used. Here, as the order of the digits is important, the technique of permutation would be used. Thus, the name 鈥渃ombination鈥� lock is inappropriate because permutation will be used to open the lock instead of combination.