Answer:

Step-by-step explanation:
cot(-11pi/6)=cot(-pi-5pi/6)= -cot(5pi/6)=cot(pi/6)=
≈1.73
Summaation of a sequence
or see a smaller scale
from 1 to 10
notice
1+10=11
2+9=11
etc
5+6=11
10/2=5
there are 5 pairs
5*11=55
so
1 to 100
1+100=101
2+99=101
...
50+51=101
100/2=50
there ar 50 pairs
50 times 101=5050
the sum is 5050
Answer:
![a)\ \ \bar x_m-\bar x_f=67.03\\\\b)\ \ E=15.7416\\\\c)\ \ CI=[51.2884, \ 82.7716]](https://tex.z-dn.net/?f=a%29%5C%20%5C%20%5Cbar%20x_m-%5Cbar%20x_f%3D67.03%5C%5C%5C%5Cb%29%5C%20%5C%20E%3D15.7416%5C%5C%5C%5Cc%29%5C%20%5C%20CI%3D%5B51.2884%2C%20%5C%2082.7716%5D)
Step-by-step explanation:
a. -Given that:

#The point estimator of the difference between the population mean expenditure for males and the population mean expenditure for females is calculated as:

Hence, the pointer is estimator 67.03
b. The standard error of the point estimator,
is calculated by the following following:

-And the margin of error, E at a 99% confidence can be calculated as:

Hence, the margin of error is 15.7416
c. The estimator confidence interval is calculated using the following formula:

#We substitute to solve for the confidence interval using the standard deviation and sample size values in a above:
![CI=\bar x_m-\bar x_f\ \pm z_{\alpha/2}\sqrt{\frac{\sigma_m^2}{n_m}+\frac{\sigma_f^2}{n_f}}\\\\=(135.67-68.64)\pm 15.7416\\\\=67.03\pm 15.7416\\\\=[51.2884, \ 82.7716]](https://tex.z-dn.net/?f=CI%3D%5Cbar%20x_m-%5Cbar%20x_f%5C%20%5Cpm%20z_%7B%5Calpha%2F2%7D%5Csqrt%7B%5Cfrac%7B%5Csigma_m%5E2%7D%7Bn_m%7D%2B%5Cfrac%7B%5Csigma_f%5E2%7D%7Bn_f%7D%7D%5C%5C%5C%5C%3D%28135.67-68.64%29%5Cpm%2015.7416%5C%5C%5C%5C%3D67.03%5Cpm%2015.7416%5C%5C%5C%5C%3D%5B51.2884%2C%20%5C%2082.7716%5D)
Hence, the 99% confidence interval is [51.2884,82.7716]
The required number is -3 which when added to the numerator and to the denominator of 5/8 results in a fraction whose value is 0.4.
<h3>What is a fraction?</h3>
Fraction is the ratio of a particular part to the whole parts of an object. A fraction has a numerator and a denominator.
<h3>Calculation:</h3>
The given fraction is 5/8
Consider a number as 'x' which is added to both the numerator and the denominator of the given fraction.
So,
(5 + x)/(8 + x)
Since it is given that the result is 0.4 i.e., 4/10, we can write
(5 + x)/(8 + x) = 4/10
⇒ 10(5 + x) = 4(8 + x)
⇒ 50 + 10x = 32 + 4x
⇒ 10x - 4x = 32 - 50
⇒ 6x = -18
⇒ x = -18/6
∴ x = -3
Therefore, the required number is -3.
Check:
(5 + (-3))/(8 + (-3)) = (5 - 3)/(8 - 3) = 2/5 = 0.4
Learn more about fractions here:
brainly.com/question/17220365
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