A teacher offers ten possible assignments for extra credit i

A teacher offers ten possible assignments for extra credit in a course but requires students to choose them, without looking, from a hat. Six assignments involve library research and four are computer programming exercises. Suppose that a student chooses two assignments, one after the other, at random without replacement. a) What is the probability that both assignments are computer programming exercises? (b) What is the probability that at least one of the assignments is a computer programming exercise?

Solution

(a) What is the probability that both assignments are computer programming exercises?

P( Both Computer Assignments) = 4 C 2 / 6 C 2 = nCr(4,2)/nCr(6,2) = 0.4

(b) What is the probability that at least one of the assignments is a computer programming exercise?

P( at least one Computer Assignments) = 1 - P( None Computer assignment chosen) = 1 - 2 C 2 / 6 C 2 = 1 - nCr(2,2)/nCr(6,2) = 1 - 0.0667 = 0.9333