Problems 1. What is the probability of getting no 2's? The definition of $0! = 1$. Same conditions as above, with a total of 10 trials. 2. Same conditions as above, with a total of 10 trials. What is the probability of getting no 2's, or one 2, or 2 2's, up to 10 2's? In other words, what's the probability of getting something? Solve this two ways, the first way is duh, it's got to be 1. The second way is to add up all the answers for the individual cases. To make this easier, take the number of trials to be $n$, and the probability of getting a 2 to be $p$. Use the binomial formula, eqn. 1.7 in reverse, and the answer should pop right out.