Question

How many possible passwords are there, given the following restrictions:

Must be between 4 and 6 characters long

Must begin with ‘A’

May only contain letters (uppercase or lowercase) and digits

		(6-4) * (26*2 + 10)
		(26*2 + 10)3 + (26*2 + 10)4 + (26*2 + 10)5
		(26*2 + 10)4 + (26*2 + 10)5 + (26*2 + 10)6
		(26*2 + 10)(6-4)

Which is true?

		Recursive algorithms are sometimes simpler than non-recursive algorithms
		Recursive algorithms are more efficient than non-recursive algorithms
		Recursive algorithms can only have one base case
		Recursive algorithms can only have one recursive case

Answer 1

1)Password contain both upper and lowe case letters =>26*2 and also contain digits =>10.

Password must be contain 4-6 digits and also given password must always starts from A.So we have length of 3-5.

So password =(26*2+10)*(3+4+5).

Answer is

(26*2 + 10)3 + (26*2 + 10)4+ (26*2 + 10)5

2)Answer is Recursive algorithms are sometimes simpler than non-recursive algorithms.

Recursive algorithms can have more than one base case and can have more than recursive case so option 3&4 are wrong.

Recursive algorithms are not effecient than non recursive algorithms.so option 2 is wrong