Solution to "Ken's M&M Truck"
This problem can be easily solved by considering extreme cases. In this problem, the extreme case is the worst case scenario. Without loss of generality, suppose Ken picks a red one first. The worst case scenario is that he does not pick a red one second. Without loss of generality, suppose he picks a green one second. Following the worst case scenario, he picks a color other than red or green on the third.. Following this reasoning, the first six M&Ms are all different colors. This is the worst case scenario. The seventh M&M, however, must be one of the original six colors. In any event, this seventh M&M will guarantee a match. The solution, therefore, is that Ken must select seven M&Ms to ensure that at least two match.