Need Help for solving probability problem

  • #1

Main Question or Discussion Point

I am new to Probability and i was unable to understand how to find i found this problem in schaum discrete mathematics book.
p(a)=0.6 p(b)=0.3 p(a and b)=0.2 how to find
(a). A but not B occurs
(b).B but not A occurs
(c).A or B occurs
(d).neither A nor B occurs
any help...

Answers and Replies

  • #2
Science Advisor
Homework Helper
Welcome to PF!

Hi srinivas2828! Welcome to PF! :wink:

Let's start with (a).

You have the probabilities of A B and AB,

and you want the probability of AB' (where ' means "not") …

so how can you combine A B and AB to give you AB' ? :smile:

(what must you subtract from A to give AB' ?)
  • #3
Science Advisor
Homework Helper
Another way to do this: Draw two overlapping circles, representing "A" and "B". The overlap is "A and B". Since P(A)= 0.6 (Please don't write "a" and "A" to mean the same thing!) the "size" of set A is .6. Since P(A and B)= 0.2 the "size" of the overlap is 0.2. What does that leave for the part of A and that is NOT in B (A and not B)?