Question

The access code for a cars security system consist of four digits the first digit cannot be 1 and the last digit must be odd how many different codes are avaiable

Answer 1

So we have 10 numbers 0 - 9
0 1 2 3 4 5 6 7 8 9
The first digit cannot be 1
therefore there are 9 possibilities
0 2 3 4 5 6 7 8 9

digits 2 and 3 can be numbers 0 through 9
therefore there are 10 possibilities for digits 2 and 3
digits 2 and 3 are a total of 2 digits
and the last digit must be odd so there are 5 possibilities -> 1 3 5 7 9
so

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