To gain access to his account, a customer using an automatic machine (ATM) must enter a five-digit code. If repetition of same five digit is not allowed (for example, 55555), how many possible combinations are there?
A) 9,990
B) 99,990
C) 6,551
D) 120
E) 240

Question

Quizplus · Accepted Answer

The total number of five-digit codes is 10^5 = 100,000. Subtract the 10 codes where all digits are the same (00000, 11111, ..., 99999), resulting in 100,000 - 10 = 99,990 possible combinations.

To Gain Access to His Account, a Customer Using an Automatic