The number of permutations of the 25 letters taken 2 at a time (with repetitions) is:

The number of permutations of the 9 digits taken 4 at a time (with repetitions) is:

Each permutation of letters can be taken with each permutation of digits, therefore the total number of possible passwords is:
Answer:
37.045
Step-by-step explanation:
Answer:
5 terms
Step-by-step explanation:
nth term of the sequence =n^2 + 20
an= n^2 + 20
1st term when n= 1
1^2 + 20= 20
2nd term n= 2
2^2 + 20=24
3rd term when n= 3
3^2 + 20= 29
4th term when n= 4
4^2 + 20= 36
5th term when n= 5
5^2 + 20 =45
6th term when n= 6
6^2 + 20=56
Hence, terms in the sequence are less than 50 are first 5 terms
answer is 525 because 775-250=525
Step-by-step explanation: