Question 1207663
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<pre>

The probability of failing exam is the COMPLEMENT to the probability of passing it.


        P(failing) = 1 - P(passing) = 1 - 0.8 = 0.2.    <U>ANSWER</U>
</pre>

Solved.



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To better memorize, &nbsp;keep in mind this joking statement:


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If the probability for a sandwich to fall butter side up is &nbsp;0.2, 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;then the probability for the sandwich to fall butter side down 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;is the &nbsp;COMPLEMENT &nbsp;to it.