Mathematical Methods in the Physical Sciences · Problem 16.1.9

FUNCTIONS OF A COMPLEX VARIABLE — Mary Boas

Mathematics — Methods · probability-boxes

Problem

You are trying to find instrument

A

in a laboratory. Unfortunately, someone has put both instruments

A

and another kind (which we shall call

B

) away in identical unmarked boxes mixed at random on a shelf. You know that the laboratory has 3

A

's and 7

B

's. If you take down one box, what is the probability that you get an

A

? If it is a

B

and you put it on the table and take down another box, what is the probability that you get an

A

this time?