Question

Exercise 2.10. Math and physics. In a class of 100 people, 60 of them are math majors, and 75 of them are physics majors. There are no students majoring in anything else in this class. This means that some of the students are double-majoring in both math and physics. A student is picked at random. What is the probability the student is double-majoring

Answer 1

Number of both = number of math + number of physics - total students:

Number of both = 60 + 75 - 100 = 35

Probability of picking on with both = 35/100 = 7/20 = 0.35 = 35%

Since the question doesn’t state what format the answer needs to be I have included the fraction, the decimal and the percentage