Question 258832
THANKS TO RICHWMILLER for pointing out the error in the failure rate value and putting in the correction: I'm not sure I'd fly in a plane with a 0.2 failure rate for the alternator. 
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P(both fail)={{{(0.2)(0.2)=0.04}}}
P(neither fail)={{{(0.8)(0.8)=0.64}}}
P(one fails)=P(first fails,second doesn't)+P(first doesn't, second fails)={{{(0.2)(0.8)+(0.8)(0.2)=0.32}}}
Ptotal={{{0.04+0.64+0.32=1}}} (all possible events are covered)