Question

Of the 11 instructors in the English department, four are new to the department and three are female. However there is only one who fits all of the descriptions. Find the probability that if you randomly choose a course taught by these instructors, you get either a new instructor or a female instructor.

Answer 1

Let us first define the two events-

A : event that a new instructor teaches the course.

B : event that a female instructor teaches the course.

Total number of instructors =11

Number of new instructors in the deparments=4

Number of instructors that are female = 3

Therefore, P(A) =4/11

P(B) = 3/11

However, there is only one who fits all of the description that is

Therefore the probability that if we randomly choose a course taught by these instructors, we get either a new instructor or a female instructor is

= 4/11 + 3/11 - 1/11

= 6/11