Question 1163616
<pre>

Ikleyn doesn't like Venn diagrams but prefers inclusion and exclusion
formulas because they are quick and easy.  I prefer Venn diagrams because
they show WHY, not just HOW.

<pre>{{{drawing(300,200,-4,4,-2,4.8,
rectangle(-4,-1.6,4,4.4), locate(-2,1.8,90),locate(1.5,1.7,20),
locate(-3.7,-1,20),
 locate(-3.6,2.5,M), locate(-.1,1.8,70),
red(circle(-sqrt(2),sqrt(2),2)),
red(circle(-sqrt(2),sqrt(2),1.95)),
red(circle(-sqrt(2),sqrt(2),1.975)),
blue(circle(sqrt(2),sqrt(2),2),circle(sqrt(2),sqrt(2),1.95),circle(sqrt(2),sqrt(2),1.975)),
locate(3.4,2.5,S)
 )}}}

Since 90+70+20=180, then 200-180 = 20 for those outside the circle.

What is the probability that an individual owns a stock? 

P(S) = (70+20)/200 = 90/200 = 9/20 = 0.45

A mutual fund?

P(M) = (90+70)/200 = 160/200 = 4/5 = 0.8

What is the probability that an individual owns neither stocks nor mutual
funds?

P(M' and S') = 20/200 = 1/10 = 0.1


What is the probability that an individual owns either a stock or a mutual
fund?

P(S or M) = (90+70+20)/200 = 180/200 = 9/10 = 0.9

or it's easier just to subtract the last answer from 1, 1 - 0.1 = 0.9

Edwin</pre>