1. The problem statement, all variables and given/known data A coin is biased so that the probability of heads is 2/3. What is the probability that exactly four heads come up when the coin is flipped seven times, assuming that the flips are independent? 2. Relevant equations 3. The attempt at a solution C(7,4)(2/3)^4(1/3)^3 = (35*16)/3^7 = 560/2187 Now, I know this answer is correct, but what if we were asked to find probability of exactly one tail followed by three heads rather than exactly four heads: How would I calculate the answer for that? Thank you.