Question

In a statistics class there are 18 juniors and 10 seniors; 6 of the seniors are females and 12 of the juniors are males. If a student is selected at random, find the probability of selecting the following: P(a junior or a senior). Enter your answer as a fraction in the form a/b (for example 2/3, 5/7) or as an integer.

Answer 1

P(a junior or a senior)=1

Explanation:

The formula of the probability is given by:

`P(A)=(n(A))/(N)`

Where P(A) is the probability of occurring an event A, n(A) is the number of favorable outcomes and N is the total number of outcomes.

In this case, N is the total number of the students of statistics class.

N=18+10=28

The probability of the union of two mutually exclusive events is given by:

`P(AUB)=P(A)+P(B)`

Therefore:

P(a junior or a senior) =P(a junior)+P(a senior)

Because a student is a junior or a senior, not both.

n(a junior)=18

n(a senior)=10

P(a junior)=18/28

P(a senior) = 10/28

P(a junior or a senior) = 18/28 + 10/28

Solving the sum of the fractions:

P(a junior or a senior) = 28/28 = 1