Answer:
Step-by-step explanation:
This is one minus the probability that all the girls audition for different roles. The total number of ways of assigning roles to the girls is 12^7, because to each of the 7 girls, you have a choice of 12 roles.
Then if each girl is to receive a different role, then there are 12!/5! possibilities for that. If you start assigning roles to the girls, then for the first girl, there are 12 choices, but for the next you have to choose one of the 11 different ones, so 11 for the next, and then one of the 10 remaining for the next etc. etc., and this is 12*11*10*...*6 = 12!/(12-7)! =12!/5!
The probability that a random assignment of one of the 12^7 roles would happen to be one of the 12!/5! roles where each girl has a different role, is
(12!/5!)/12^7 = 12!/(12^7 5!)
Then the probability that two or more girls addition for the same part is the probability that not all the girls are assigned different roles, this is thus:
1 - 12!/(12^7 5!)
I FOUND YOUR COMPLETE QUESTION IN OTHER SOURCES.
PLEASE SEE ATTACHED IMAGE.
First, we define the variables:
x: number of years after 1950
f (x): amount of vinyl sold.
Then, with the variables defined, we have:
68594 vinyl records were sold in 1958 ---------> f (8) = 68594
91299 vinyl records were sold in 1961 ---------> f (11) = 91299
38720 vinyl records were sold in 1952 ---------> f (2) = 38720
161743 vinyl records were sold in 1967 ---------> f (17) = 161743
Answer:
b is the answer in your questions