Geometry Homework

Question

In a class of 39 students, 15 own a iPhone, 10 own a iPad and 2 own both. What is the probability that a student chosen at random owns either an iPhone or an iPad?

A. 12/15

B. 27/30

C. 5/6

D. 23/30

Answer 1

The number of students in class is 39. 15 have iPhone.

P(iPhone) = 15/39.

Similarly,

P(iPad) = 10/39.

We also have two students that own both.

P(iPhone and iPad) = 2/39.

Now we use the formula

P(iPhone or iPad) = P(iPhone) + P(iPad) - P(iPhone and iPad).

Which answer will be?