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Question

4) Best Buddies have 60 students, and 20 students are 12^th graders

 

A) What is the probability of 2 students who are 12 graders with replacement?

B) What is the probability of 2 students who are 12 graders without replacement?

C) If 15 random students join Best Buddies, what is the probability that they are 12^th graders?

 

Answer 1

Step 1:

4A)

Total number of students in best buddies are 60.

Among them 20 students are 12^th graders.

Out of 60 students 2 students are selected randomly.

Find the probability that the 2 students are from 12^th graders.

Assume that the 2 selections are made with replacement.

Let the two events be .

Probability of selecting first student : .

Probability of selecting second student : .

The two events are independent events then .

Probability of selecting 2 students is

Probability of selecting 2 students from 60 students who are 12^th graders with replacement is 0.1111.

Solution:

Probability of selecting 2 students from 60 students who are 12^th graders with replacement is 0.1111.

Answer 2

Step 1:

4B)

Find the probability that the 2 students are from 12^th graders.

Assume that the 2 selections are made without replacement.

Let the two events be .

Probability of selecting first student : .

Probability of selecting second student : .

The two events are independent events then .

Probability of selecting 2 students is

Probability of selecting 2 students from 60 students who are 12^th graders without replacement is 0.1073.

Solution:

Probability of selecting 2 students from 60 students who are 12^th graders without replacement is 0.1073.