Suppose you roll a die 30 times. How many 2s would you expect to get?

Answer 1

This is an expected value problem. The expected value formula is Σ x P(x). Given that we are rolling a die 30 times and the probability of rolling a 2 is 1/6 we can simply sum up 1/6 30 times. In other words we can do 1/6 * 30 = 5. So we would expect to roll a 2 5 times in 30 rolls