A five-digit integer will be chosen at random from all possible positive five-digit integers. What is the probability that the number's units digit will be less than 5? Express your answer as a common fraction.

The number of five-digit integers with units digit less than 5 is 36,000.

The number of five-digit integers is 90,000.

Therefore, the probability is 36,000/90,000 = 2/5.

There are 90,000 5-digit integers:

1/2 of 90,000 ==45,000 will end in {0, 1, 2, 3, 4}

Therefore, the probability is ==45,000 / 90,000 ==1 / 2