Final answer:
a. There are 0.0001161048 ways to select 15 cases from 6 varieties. b. There are 504 ways to select 15 cases if the employee orders at least 1 of each variety.
Step-by-step explanation:
a. To select 15 cases from 6 varieties, you can use the concept of combinations. The formula to calculate the number of ways to select r items from a set of n items is nCr = n! / (r! * (n-r)!).
In this case, the number of ways to select 15 cases from 6 varieties is
6C15 = 6! / (15! * (6-15)!)
= 6! / (15! * (-9)!)
= 6! / (15! * 9!)
= (6 * 5 * 4 * 3 * 2 * 1) / (15 * 14 * 13 * 12 * 11 * 10 * 9!)
= 720 / (130 * 12 * 11 * 10 * 9!)
= 720 / (171600 * 9!)
= 720 / (171600 * (9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1))
= 720 / (171600 * 362880)
= 720 / 62270208000
= 1 / 8610
= 0.0001161048
b. To select 15 cases if the employee orders at least 1 of each variety, we can first distribute 1 case of each variety. Then, we have 9 cases left to distribute. Using the concept of combinations, the number of ways to distribute these 9 cases among 6 varieties is 9C6 = 9! / (6! * (9-6)!)
= 9! / (6! * 3!)
= (9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1) / (6 * 5 * 4 * 3 * 2 * 1 * 3 * 2 * 1)
= 9 * 8 * 7 / 3 * 2 * 1
= 504