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Need Help for solving probability problem

  1. Jul 11, 2009 #1
    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...
  2. jcsd
  3. Jul 11, 2009 #2


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    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' ?)
  4. Jul 11, 2009 #3


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    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)?
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