SOLUTION: There are 4 freshman, 6 sophomores, 7 juniors, and 3 seniors on a school field trip. If three students are randomly selected to carry water bottle cases, what is the probability th
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-> SOLUTION: There are 4 freshman, 6 sophomores, 7 juniors, and 3 seniors on a school field trip. If three students are randomly selected to carry water bottle cases, what is the probability th
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Question 1116313: There are 4 freshman, 6 sophomores, 7 juniors, and 3 seniors on a school field trip. If three students are randomly selected to carry water bottle cases, what is the probability that they are all juniors?
Would it be 7/13? Answer by ikleyn(52781) (Show Source):
In all, there are 4 + 6 + 7 + 3 = 20 students.
By selecting randomly 3 students of 20, you can do it in = = 1140 ways.
In how many ways can you select the group of 3 juniors ?
You select them from the sub-group of 7 junior students, therefore, you can do it in = = 35 ways.
Therefore, the probability under the question is this number = 0.031 = 3.1%.
In order to solve freely such problems, you need to know about Combinations.
