Question

Suppose that in a class of 50 students, 5 students have perfect attendance and 4 students fail. Exactly one student with perfect attendance fails the class. [Assume that everyone either fails or passes the class; no incomplete grades.]

e) What is the probability that a student passes the class and has perfect

attendance?

f) What is the probability that a student misses at least one day of class?

Answer 1

We are given here that:

n(total) = 50
n(perfect attendance) = 5
n(failed students) = 4
n(perfect attendance and failed) = 1 which means that n(perfect attendance and passed ) = 5 - 1 = 4

e) Probability that a student passes the class and has perfect attendance

n(perfect attendance and passed the class) / n(total)

= 4/50

= 0.08

Therefore 0.08 is the required probability here.

b) Probability that a student misses at least one day of the class

= 1 - Probability that the student has perfect attendance

= 1 - (5/50)

= 45/50

= 0.9

Therefore 0.9 is the required probability here.