ATM pin codes consist of fourdigit sequences of numbers from

ATM pin codes consist of four-digit sequences of numbers from 0 to 9.   1. Find the total numbers of ATM possibe.      2. Find the total number of ATM codes if the first digit is not a zero. (Show steps)

Solution

4 digits....

Each digit can be any of the 10 possibilities(0,1,2,3,4,5,6,7,8,9)

So, for the first digit, we have 10 possibilities
For the second, 10
etc etc

So, total no of possibilities :
10*10*10*10

10^4 or 10000

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2)
First digit aint 0

So, the first digit has only 9 possibilities

So,
9*10*10*10

9*1000

9000 ---> ANSWER