Question

fifthy percent of students read the newspaper, 40 percent read the journal, and 30 percent read both. Fin the probability that a randomly selected student reads the local paper given that the student reads only one of the two papers

Answer 1

30%

Answer 2

To make work easy assume a sample set of 100 students.
50 read the paper,
40 read the journal
30 read both.
That means out of the 50 that read the paper, 30 read the journal while 20 do not.These 20 only read the paper.
Similarly out of the 40 that read the journal,30 read the paper and 10 do not.
So the total number who read either the paper or the journal are
20+10=30.
Now 30 out of 100 read only one them,so we get
30%