Question

The access code for a​ car's security system consists of four digits. the first digit cannot be 6 and the last digit must be even. how many different codes are​ available?

Answer 1

There are 9 choices for the first digit: {0, 1, 2, 3, 4, 5, 7, 8, 9}
There are 10 choices for the second digit: {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
There are 10 choices for the third digit: {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
There are 5 choices for the fourth digit: {0, 2, 4, 6, 8}

Multiply the number of choices per digit to get: 9*10*10*5 = 90*50 = 4500

Answer: 4500