The first three positive composite numbers are 4, 6, and 8. To find the units digit of their product, I only need to multiply the units digits of each number, since the other digits will not affect the final units digit. So I have 4 times 6 times 8, which is 24 times 8. The units digit of 24 is 4, and the units digit of 8 is 8, so I multiply 4 by 8 to get 32. The units digit of 32 is 2, which is the final answer. 
What is the units digit of the product of the first three positive composite numbers?