Answer:
i'm pretty sure the one you have selected in the photo is right
Step-by-step explanation:
If x represents the mass of 1 ball in kg, then the balance shows ...
... 6x = x + 9 kg
... 5x = 9 kg
Then 6x is ...
... (6/5)·5x = (6/5)·9 kg = 10.8 kg
0.8 kg = 0.8·1000 g = 800 g
so 10.8 kg is ...
... D. 10 kg 800 g
Answer:
years worked: 14
at least 10 years: 73%
Step-by-step explanation:
The mean is found by adding the years of service and dividing by the number of employees. The total years of service is 417, so the average is ...
average years worked = 417/30 = 13.9 ≈ 14 . . . years
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The percentage of employees that have worked there at least 10 years is found by counting the number with 10 or more years of service and dividing that count by the total number of employees. The result is then expressed as a percentage.
(10 years or over)/(total number) = 22/30 = 0.73_3 (a repeating decimal) ≈ 73%
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Comment on the working
A spreadsheet can be helpful for this. It has a function that can calculate the mean for you. Sorting the years of service into order can make it trivially easy to count the number that are 10 or more, or you can write a function that will do the count for you. (Also, less than 10 means the years are a single digit. There are 8 single-digit numbers in your list.) The hard part is copying 30 numbers without error.
Answer:
The margin of error is of 0.3012, and it means that we should be 99% confident that the population mean would be within 0.3012 of the sample mean.
Step-by-step explanation:
Margin of error
In which 
is the standard deviation and n is the size of the sample.
Standard deviation of 1.3
This means that 
She surveys 124 families
This means that 
Margin of error and meaning:
The margin of error is of 0.3012, and it means that we should be 99% confident that the population mean would be within 0.3012 of the sample mean.
