How many 4-digit numbers have the second digit even and the fourth digit even? (Here, digits are read from the left, so the first digit is the leftmost digit, and so on.)
1 2 3 0
You have 9 choices for the first number==9
You have 5 choices for the 2nd number ==5
You have 10 choices for the 3rd number==10
You have 5 choices for the 4th number ==5
Therefore, there are: 9 x 5 x 10 x 5 ==2,250 such numbers.