Question: Melissa must finish two courses, statistics and economics, in order to complete requirements for a degree. All along she has mainttaned an 80% average. She has calculated probabilities of scoring in the remaining two courses as follows:

probabilities of scoring 80 in statistics =0.80

probability of scoring 80 in economics =0.40

probability of scoring 80 in both = 0.30

a. What is the probability that she will score 80 in at least one of her courses?
b. What is the probability that she will not score 80 in either course?

Thanks in advance

Edwim,

I will give formulas for them. It is similar to the other question you posted.

a.
P(at least one)=P(stats or econ)
=P(stats)+P(econ)-P(stats and econ)

b.
P(neither stats nor econ)=1-P(at least one)

Many thanks Quark. Edwim12