From a survey of 100 college students, a marketing research company found that 50 students owned iPods, 50 owned cars, and 20 owned both cars and iPods.
http://awwapp.com/s/76/cb/3c.html
http://surfari.editme.com/files/VennDiagram/Venn%20Diagram.jpg
50-20 = 30 owned only cars
50-20 = 30 owned only iPods
That leaves 20 outside the diagram boundaries, owning neither iPod nor car
30 car only
30 iPod only
20 both, intersection of circles
20 outside, own neither
20
To find the number of students who own either cars or iPods, we need to use the principle of inclusion-exclusion.
Step 1: Add the number of students who own cars and those who own iPods:
Number of students with cars + Number of students with iPods = 50 + 50 = 100
Step 2: Subtract the number of students who own both cars and iPods (20) since we have counted them twice in Step 1:
Number of students with cars or iPods = Number of students with cars + Number of students with iPods - Number of students with both cars and iPods
Number of students with cars or iPods = 100 - 20 = 80
Therefore, out of the 100 college students surveyed, 80 students own either cars or iPods.