Answer:
The 90% confidence interval for the population mean iron concentration is between 0.167 cc/m³ and 0.195 cc/m³.
Step-by-step explanation:
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
So it is z with a pvalue of
, so 
Now, find M as such

In which
is the standard deviation of the population and n is the size of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 0.181 - 0.0140 = 0.167 cc/m³.
The upper end of the interval is the sample mean added to M. So it is 0.181 + 0.0140 = 0.195 cc/m³.
The 90% confidence interval for the population mean iron concentration is between 0.167 cc/m³ and 0.195 cc/m³.
3(x+5)=39
3 * x + 3 * 5 = 39
3x + 15 = 39
3x = 39 - 15
3x= 24
x = 8
Answer:
1/3
Step-by-step explanation:
3x3= 9
Make 3/9 a fraction and simplify it and it would give you 1/3
Here the given expression is

We need to find the value of y when x =3 . So we substitute the value of x in the given expression.

So when x=3, y=0.4 and that's the required answer.
Yeah because he was at least 80% and when you add the grain and carbon that was total. Then divide the carbon. It will be 80%