Let S be the set of all passwords which are six to eight characters long, where each character is either an alphabet from {A, B, C, D, E} or a number from {1, 2, 3, 4, 5} with the repetition of characters allowed. If the number of passwords in S whose at least one character is a number from {1, 2, 3, 4, 5} is , then is equal to ______.
← JEE Main 2022 · 28 Jul · Shift 1
MathematicsInteger+4 / -1Question 21 of 90
JEE Main 2022 · 28 Jul · Shift 1, Mathematics question 21
Answer and worked solution
Official answer: 7073
Complement. Passwords of length n with at least one digit: .
Sum over n = 6, 7, 8, divided by : .
Answer: 7073