A shoebox holds a number of disks of the

Question

A shoebox holds a number of disks of the

same size. There are 5 red, 6 white, and
7 blue disks. You pick out a disk, record
its color, and return it to the box. If you
repeat this process 250 times, how many
times can you expect to pick either a red
or white disk?

Answer 1

There are a total of 5 + 6 + 7 = 18 disks in the box. The probability of picking a red or white disk on any one draw is (5 + 6) / 18 = 11/18. Since each draw is independent, the number of times you can expect to pick a red or white disk in 250 draws follows a binomial distribution with n = 250 and p = 11/18. The expected value of this distribution is np = 250 * 11/18 = 154. Therefore, you can expect to pick a red or white disk approximately 154 times.