In cylindrical coordinates, we have
, so that

correspond to the upper and lower halves of a sphere with radius
. In spherical coordinates, this sphere is
.
means our region is between two cylinders with radius 1 and
. In spherical coordinates, the inner cylinder has equation

This cylinder meets the sphere when

which occurs at

where
. Then
.
The volume element transforms to

Putting everything together, we have

3(x - 25) < $100. We're not req'd to solve this.
Answer:
it's probably ours it's just a lucky guess
Step-by-step explanation:
Answer: A. X= -5, Y= 3, Z= 4
Step-by-step explanation:
Answer:
And if we solve for a we got
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the hourly rates of a population, and for this case we know the distribution for X is given by:
For this part we want to find a value a, such that we satisfy this condition:
(a)
(b)
Both conditions are equivalent on this case. We can use the z score again in order to find the value a.
As we can see on the figure attached the z value that satisfy the condition with 0.80 of the area on the left and 0.20 of the area on the right it's z=0.842. On this case P(Z<0.842)=0.8 and P(z>0.842)=0.20
If we use condition (b) from previous we have this:
But we know which value of z satisfy the previous equation so then we can do this:
And if we solve for a we got