Question

Amit Kumar got a 4-digit pass code (which is formed out of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9) of his ATM card from ICICI Bank. Butafter the 50th day he lost the pass code and also forgot the number. How many maximum number of trials may he have to take to get the right number? 0 can be the beginning of the code number.

• A. $\texttt{10!}$
• B. 104
• C. 94
• D. $\texttt{9!}$

Answer 1

Answer: (B)

104

Answer 2

Since the pass code it is a 4 code,
The first digit will be : 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, it can be any of the following. So 10 ways to get first number
The second digit will be : 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, it can be any of the following. So 10 ways to get second number
The third digit will be : 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, it can be any of the following. So 10 ways to get third number
The fourth digit will be : 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, it can be any of the following. So 10 ways to get fourth number
So There will be around 104 number of trials to get the right code.
The correct option is (B)