Imagine that the first traffic light you encounter on your way to school each morning has a 60 s cycle in which it is green for 20 s. What is the probability that you will get a green light on the next three morning trips to school? I get the answer this way but i dont get why. C(5,3) x (1/3)^3 I have two more questions they are similar but they are hard to post. Since i cant really post this arrangement in a triangle i'll just describe it. There are 4 H's at the base of a triangle, then there are 3 T's above those and then 2 A's and then at the tip of the triangle there is an M. Determine the number of paths that spell math, you have to start from the top and you can only move diagonally. I can figure out the answer my self which is 8 but i dont get why. The reason why im asking this is because there is a question similar to this where you have to spell mathematics, but its not in the shape of a triangle, its in the shape of a diamon sort of. So how would I work this out.