A die is rolled nine times and the number of times that two shows on the upper face is counted. If this experiment is repeated many​ times, find the mean for the number of twos.

Step-by-step explanation:

Given

-- number of rolls

Required

The mean of 2's

The distribution follows binomial distribution where:

In this case:

---- the theoretical probability of rolling 2

So, the mean of 2's is calculated using:

Simplify

or