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MrMuchimi
3 years ago
14

Use the Midpoint Rule with n = 5 to estimate the volume V obtained by rotating about the y-axis the region under the curve y = 1

+ 9x3 , 0 ≤ x ≤ 1. (Round your answer to two decimal places.)
Mathematics
1 answer:
velikii [3]3 years ago
3 0

Using the shell method, the volume is given exactly by the definite integral,

2\pi\displaystyle\int_0^1x(1+9x^3)\,\mathrm dx

Splitting up the interval [0, 1] into 5 subintervals gives the partition,

[0, 1/5], [1/5, 2/5], [2/5, 3/5], [3/5, 4/5], [4/5, 5]

with left and right endpoints, respectively, for the i-th subinterval

\ell_i=\dfrac{i-1}5

r_i=\dfrac i5

where 1\le i\le5. The midpoint of each subinterval is

m_i=\dfrac{\ell_i+r_i}2=\dfrac{2i-1}{10}

Then the Riemann sum approximating the integral above is

2\pi\displaystyle\sum_{i=1}^5m_i(1+9{m_i}^3)\frac{1-0}5

\dfrac{2\pi}5\displaystyle\sum_{i=1}^5\left(\frac{2i-1}{10}+9\left(\frac{2i-1}{10}\right)^4\right)

\dfrac{2\pi}{5\cdot10^4}\displaystyle\sum_{i=1}^5\left(16i^4-32i^3+24i^2+1992i-999\right)=\frac{112,021\pi}{25,000}\approx\boxed{14.08}

(compare to the actual value of the integral of about 14.45)

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An image formed by a circular spotlight has a radius of 124 centimeters. What is the area of the circular image? Use 3.14 for pi
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area = pi X radius squared

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= 3.14 x 15376 = 48,280.64 square centimeters.

5 0
2 years ago
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Suppose that the mean water hardness of lakes in Kansas is 425 mg/L and these values tend to follow a normal distribution. A lim
tino4ka555 [31]

Answer:

The mean water hardness of lakes in Kansas is 425 mg/L or greater.

Step-by-step explanation:

We are given the following data set:

346, 496, 352, 378, 315, 420, 485, 446, 479, 422, 494, 289, 436, 516, 615, 491, 360, 385, 500, 558, 381, 303, 434, 562, 496

Formula:

\text{Standard Deviation} = \sqrt{\displaystyle\frac{\sum (x_i -\bar{x})^2}{n-1}}  

where x_i are data points, \bar{x} is the mean and n is the number of observations.  

Mean = \displaystyle\frac{\text{Sum of all observations}}{\text{Total number of observation}}

Mean =\displaystyle\frac{10959}{25} =438.36

Sum of squares of differences = 175413.76

S.D = \sqrt{\dfrac{175413.76}{24}} = 85.49

Population mean, μ = 425 mg/L

Sample mean, \bar{x} = 438.36

Sample size, n = 25

Alpha, α = 0.05

Sample standard deviation, s = 85.49

First, we design the null and the alternate hypothesis

H_{0}: \mu \geq 425\text{ mg per Litre}\\H_A: \mu < 425\text{ mg per Litre}

We use one-tailed t test to perform this hypothesis.

Formula:

t_{stat} = \displaystyle\frac{\bar{x} - \mu}{\frac{s}{\sqrt{n}} }

Putting all the values, we have

t_{stat} = \displaystyle\frac{438.36 - 425}{\frac{85.49}{\sqrt{25}} } = 0.7813

Now, t_{critical} \text{ at 0.05 level of significance, 24 degree of freedom } = -1.7108

Since,                        

The calculated t-statistic is greater than the critical value, we fail to reject the null hypothesis and accept it.

Thus, the mean water hardness of lakes in Kansas is 425 mg/L or greater.

6 0
3 years ago
A certain statistic d hat is being used to estimate a population parameter D. The expected value of d hat is not equal to D. Wha
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Answer:

the correct option is E. d is biased.

Step-by-step explanation:

As given,

The expected value of d hat is not equal to D.

We know that,

The unbiased-ness is the property that tells the expected value of d is equal to D

So, the correct option is E. d is biased.

5 0
3 years ago
Selma uses a jogging trail that runs through a park near her home. The trail is a loop that is of a mile long. On Monday, Selma
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Answer:

4.5 miles per hour

Step-by-step explanation:

Selma uses a jogging trail that runs through a park near her home. The trail is a loop that is 3/4 of a mile long. On Monday, Selma ran the loop in 1/6 of an hour. What is Selma's unit rate in miles per hour for Monday's run?

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Time taken on Monday = 1/6 of an hour.

What is Selma's unit rate in miles per hour for Monday's run?

Unit rate in miles per hour for Monday's run = distance ÷ time taken

= 3/4 ÷ 1/6

= 3/4 × 6/1

= (3 * 6) / (4 * 1)

= 18/4

= 4.5 miles per hour

Unit rate in miles per hour for Monday's run = 4.5 miles per hour

3 0
3 years ago
Which of the following angles is in the solution set of sec^2θ - 3secθ - 2 = 0 for 0° ≤ θ &lt; 360°.
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1 / cos^2 O - 3 / cos O - 2 = 0
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O = 74 degrees  (from  0.2807) another solution is 360-74 =  286 degrees

Its D
4 0
3 years ago
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