document.write( "Question 1137843: Let P(A) = 0.6, P(B) = 0.3 and P(A / B) = 0.5. Find P(A or B). \n" ); document.write( "

Algebra.Com's Answer #755734 by ikleyn(52777) $\"\"$ $\"About$

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document.write( "P(A | B)  actually means and is the same as  P(A & B)/P(B),  where &  represents the logical  \"AND\", or the intersection of the two sets.\r\n" );
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document.write( "Therefore, the given  P(A | B) = 0.5  means that  P(A & B)/P(B) = 0.5.\r\n" );
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document.write( "Multiplying both sides of the last equality by P(B), you get\r\n" );
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document.write( "    P(A & B) = 0.5*P(B) = 0.5*0.3 = 0.15.\r\n" );
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document.write( "Now last step is to use the general formula\r\n" );
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document.write( "    P(A or B) = P(A) + P(B) - P(A & B) = 0.6 + 0.3 - 0.15 = 0.75.    ANSWER\r\n" );
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