Question

There are 500 students in Davis MiddleSchool. Out of 10 students in a randomsurvey, 2 have last names that beginwith the letter "A." In another randomsurvey of 10 students in the sameschool, 8 passed their most recent mathquiz.From this data, how many students inthe whole school could reasonably beexpected to have a last name beginningwith "A" and also have passed their mostrecent math quiz?

Answer 1

The probability that a student have last names that begin with the letter "A" is 2/10 = 1/5

The probability that a student passed their most recent math quiz is 8/10 = 4/5

Then, the probability that a student have a last names that begin with the letter "A" and passed their most recent math quiz is 1/5 x 4/5 = 4/25

Since there are 500 students in the school, approximately 4/25 x 500 = 80 of them have a last names that begin with the letter "A" and passed their most recent math quiz.