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:
Please check the explanation.
Step-by-step explanation:
Given
a)
f(x) + g(x) = (2x - 1) + (2 - x)
= 2x -1 + 2 - x
= x + 1
b)
f(x) - g(x) = (2x - 1) - (2 - x)
= 2x - 1 - 2 + x
= 3x - 3
c)
g(-5) - f(-5)
Putting x = -5 in g(x) = 2 - x
g(x) = 2 - x
g(-5) = 2 - (-5) = 2+5 = 7
Putting x = -5 in f(x) = 2x - 1
f(x) = 2x - 1
f(-5) = 2(-5) - 1
= -10 - 1
= -11
Thus,
g(-5) - f(-5) = 7 - (-11) = 7+11 = 18
d)
f(x).g(x) = (2x - 1) (2 - x) = -2x² + 5x - 2
e)
f(g(x)) = f(2-x)
= 2(2-x)-1
= 4-2x-1
= 3-2x
Step-by-step explanation:
the rate of change is the slope of the line connecting both points.
the slope is the ratio y/x indicating how many units y changes, when x changes a certain amount of units when going from one point to another.
so, here
x changes by -10 units (from -24 to -34)
y changes by -10 units (from 60 to 50).
the slope or rate of change is -10/-10 = 1/1 = 1
(1)
given 
= 
( cross- multiply )
10j = 54 ( divide both sides by 10 )
j = 
= 
← in simplest form
(9)
let h be the hours worked daily , then
3h = 20 
= 
( divide both sides by 3 )
h = ÷ 3
= × 
= 
= 6 
She worked 6 hours each day
Answer:
x = 10/√2 ≈ 7.07
Step-by-step explanation:
Comenzaremos por dividir el triángulo en dos partes y definir H, como en la figura adjunta.
Aplicando el teorema de Tales, sabemos que:
También sabemos que, dado que el tirángulo menor es la mitad que el triángulo mayor, la relación entre áreas es:
Dado que formamos dos triángulos rectángulos, podemos despejar el valor de H como:
Podemos entonces despejar x de la siguiente manera:
