How many students know how to use both kinds of computers?

Question

In a group of 140 students, 85 know how to use a Macintosh, 100 know how to use an IBM-compatible computer, and 10 do not know how to use either kind. How many students know how to use both kinds of computers?

 

a. 75
b. 40
c. 55
d. 90
e. 130

Answer 1

P(A)= 85

P(B)= 100

 

Now, 10 do not know how to use either kind. That is P(AUB) ^complement

 

To get P(AUB), we can subtract from the total number of students which is the sample space.

 

P(AUB) =  140-10 =130

 

Now we need to find P(A intersection B) =  P(A)+P(B)-P(AUB) = 85+100-130 = 55

 

So, 55 students know how to use both kinds of computers.