Answer:
A. 7 in.
Step-by-step explanation:
We have been given that the perimeter of a rectangle is 16 inches. The equation that represents the perimeter of the rectangle is , where l represents the length of the rectangle and w represents the width of the rectangle.
We know that perimeter of rectangle is 2 times the sum of width and length of rectangle.
To be a rectangle length cannot be 8 as length and width of the rectangle is 8 inches.
Therefore, 7 inches the possible value for the length of the rectangle.
The question is incomplete! Complete question along with answer and step by step explanation is provided below.
Question:
The lifetime (in hours) of a 60-watt light bulb is a random variable that has a Normal distribution with σ = 30 hours. A random sample of 25 bulbs put on test produced a sample mean lifetime of = 1038 hours.
If in the study of the lifetime of 60-watt light bulbs it was desired to have a margin of error no larger than 6 hours with 99% confidence, how many randomly selected 60-watt light bulbs should be tested to achieve this result?
Given Information:
standard deviation = σ = 30 hours
confidence level = 99%
Margin of error = 6 hours
Required Information:
sample size = n = ?
Answer:
sample size = n ≈ 165
Step-by-step explanation:
We know that margin of error is given by
Margin of error = z*(σ/√n)
Where z is the corresponding confidence level score, σ is the standard deviation and n is the sample size
√n = z*σ/Margin of error
squaring both sides
n = (z*σ/Margin of error)²
For 99% confidence level the z-score is 2.576
n = (2.576*30/6)²
n = 164.73
since number of bulbs cannot be in fraction so rounding off yields
n ≈ 165
Therefore, a sample size of 165 bulbs is needed to ensure a margin of error not greater than 6 hours.
Answer: x^2 + 9x + 20
Step-by-step explanation:
Foil Method: (a + b) (c + d) = ac + ad + bc + bd
Lets say:
a = x
b = 5
c = x
d = 4
Plugging in the numbers: xx + 4x + 5x + 5*4
Combine like terms:
xx = x^2
4x + 5x = 9x
5 * 4 = 20
You're then left with: x^2 + 9x + 20
Answer:
After taking the first exam, 15 of the students dropped the class. The value 15 describes a characteristic of a population - first choice.
