Ello ello! I'm not sure how they are getting 5/16 as the answer. The question is: Suppose you take a true/false quiz consisting of four questions, each worth 25%. If a score of 50% or less fails the quiz, what is the probabillity that you can pass the quiz by randomly guessing each answer? Well here is how I broke it down... If you get a 50% or less you fail, so you need at least 3 out of the 4 right to get a 75%. I then thought, how many possible outcomes are there? Well its like tossing a coin, its either Head or Tails or in this case True or False so you have: 2^4 = 16 possible outcomes. Now I thought to use combinations, you want 4 choose 3, Step 1: Choose first question (T or F) Step 2: Choose 2nd question (T or F) Step 3: choose 3rd qustion (T or F) Step 4: choose 4th question (T or F) but I soon realized I dont' think i can apply the multiplication rule on this, there are too many cases so i tried combinations and i said: 4 choose 3 = 4. So the probabily i said was: 4/16 = 1/4. But the answer is 5/16. ANy ideas?