A box contains 9 balls marked 1 to 9. Four balls are drawn in succession without replacement. Determine the probability that the four-digit number formed is: a. even b. greater than 5000 c. an odd number less than 3000

a. Just look at the units digit to verify whether or not it's even. Essentially, it reduces the problem to the probability that the units digit is even. As such, the probability is just 4/9 (since there are 4 even numbers from 1-9)