P(most favorable outcome) = 1 -(0.03 +0.16 -0.01) = 0.82
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"repair fails" includes the "infection and failure" case, as does "infection". By adding the probability of "repair fails" and "infection", we count the "infection and failure" case twice. So, we have to subtract the probability of "infection and failure" from the sum of "repaire fails" and "infection" in order to count each bad outcome only once.
The probability of a good outcome is the complement of the probability of a bad outcome.
62 + 22 = 84 total light strings.
36 bulbs/string multiplied by 84 light strings = 3,024 total light bulbs
For this question , you just need to divide 1 7/8 with 1/12
1 7/8 : 1/12
= 15/8 : 1/12
= 15/8 x 12/1
= 22.5 bags.
So i guess she can make around 22 full bags
hope this helps
