So, the first number can be any of the 10 digits (0-9). From these 10 digits, 0,2,4,6, and 8 are even numbers. The total number of even numbers is 5. Therefore, 5 numbers are not even numbers.
So, the probability that a first character is an even number is equal to the number of even divided by the total number of possible outcomes. That is,

The probability is
0.50.