Multiply 1/8 x 3/4 =
2 answers:
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Answer:
If the lifetime of batteries in the packet is 40.83 hours or more then, it exceeds for 5% of all packages.
Step-by-step explanation:
We are given the following information in the question:
Mean, μ = 15
Standard Deviation, σ = 1
Sample size = 4
Total lifetime of 4 batteries = 40 hours
We are given that the distribution of lifetime is a bell shaped distribution that is a normal distribution.
Formula:
Standard error due to sampling:
We have to find the value of x such that the probability is 0.05
P(X > x) = 0.05
Calculation the value from standard normal z table, we have,
Hence, if the lifetime of batteries in the packet is 40.83 hours or more then, it exceeds for 5% of all packages.
To solve this problem you have to set up a proportion. To form one side of the proportion you use "is over of" meaning what number represented by is, in this case 18, is placed over the number represented by of, 3000. 
Since you are finding the percent of something, youre x value is placed above "100" because percent values are most commonly out of 100%. 
So now your proportion will look like To solve the proportion you cross multiply and divide. So you multiply 100 and 18 since they are crossed from each other, then divide 1800 by 3000. The answer is .6. 18 is .6% of 3000.
So now your proportion will look like