Problem Solving

Nine cards numbered from 1 to 9 are placed in an empty bowl. Four cards are drawn from the bowl one-by-one without replacement to form a four-digit number (the first card gives the thousands digit, the second card gives the hundreds digit, the third card gives the tens digit and the fourth card gives the units digit). What is the probability that the four-digit number is even?

A. 1/9
B. 2/9
C. 3/9
D. 4/9
E. 5/9

Answer: D

Source: GMAT Club Tests

What is the probability that the four-digit number is even?
First card = thousand digit
Second card = hundred digit
Third card = tens digit
Fourth card = unit digit

The fourth card will be used to determine if the number is even or not.
Since total cards = 9, the fourth card has a 1/9 chance of each digit and for all the four digits, it's going to be =>
$$\frac{1}{9}+\frac{1}{9}+\frac{1}{9}+\frac{1}{9}=\frac{4}{9}\ chance\ of\ its\ being\ even.$$
Answer = option D