Question

Dr. Zadok's Museum has a collection of cameras. If a camera is selected at random from the museum's collection, the probability that it is digital is 0.43 and the probability that it is a single lens reflex (SLR) camera is 0.51. The probability that the randomly selected camera is both digital and an SLR is 0.19. Let the event that a camera is digital be D and the event that a camera is an SLR be S. Suppose that a camera is selected at random from the museum's collection. Find the probability that it is either digital or an SLR.

Answer 1

0.56

Explanation:

We can draw a Venn diagram.

Assume there are 100 cameras in the collection.

p(D) = 0.43

43 cameras are digital

p(S) = 0.51

51 cameras are SLR

p(both) = 0.19

19 cameras are both digital and SLR

43 - 19 = 24

24 cameras are digital but not SLR

19 cameras are both digital and SLR

51 - 19 = 32

32 cameras are SLR but not digital

p(D or S) = (24 + 32)/100 = 0.56