Answer:
d. 9x + 63 and 63 square feet
Step-by-step explanation:
Given
Original
Extended
Required
Determine an expression and the value of the extended area
First, we calculate the area of the original desk
From the given parameters, we have:
--- area of the new surface
Open bracket
The area of the new surface is the summation of the area of the original desk and the area of the extended portion (E)
So:
Make E the subject
Hence, the area of the extended portion is 63
Answer:
The value of height that separates the bottom 90% of data from the top 10% is 3.507.
Step-by-step explanation:
1) 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".
2) Solution to the problem
Let X the random variable that represent the grades of a population, and for this case we know the distribution for X is given by:
Where and
And the best way to solve this problem is using the normal standard distribution and the z score 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 0.90 of the area on the left and 0.10 of the area on the right it's z=0.816. On this case P(Z<0.816)=0.90 and P(Z>0.816)=0.1
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
So the value of height that separates the bottom 90% of data from the top 10% is 3.507.