2. You are in a completely dark room with a drawer containing 10 red, 20 blue, 30 green, and 40 khaki socks. What is the smallest number of socks you must randomly pull out in order to be sure of having at least one of each color?
Solution: 91 . The maximum number of socks that can be pulled out without representing every color is 20 blue +30 green +40 khaki $=90$, so 91 is the minimum needed to ensure that this doesn't happen.