00:01
In this problem, it is said that a certain password consists of two lowercase letters followed by four digits.
00:07
We want to determine how many different passwords are possible if repetition of letters and digits is not allowed.
00:12
So, first of all, there will be two lowercase letters and then there will be one, two, three, four digits.
00:20
So, how many letters, how many lowercase letters are there? there are a total of 26 letters in the english alphabet, so there are 26 different ways of selecting this first letter.
00:31
And since the repetition of letters and digits is not permitted, that means that the second letter will be any one of the 26 letters except for the letter selected over here.
00:39
So, we have 26 minus 1, a total of 25 different options for this letter.
00:44
Now, next we have a digit.
00:45
There are 10 digits from 0 to 9, so there are 10 options for this digit...