What is the minimum sample size required to estimate a population mean with 90% confidence when the desired margin of error is 1.25

Answers

Answer 1

Complete Question

What is the minimum sample size required to estimate a population mean with 90% confidence when the desired margin of error is 1.25? The standard deviation in a pre-selected sample is  7.5

Answer:

The minimum sample size is  [tex]n =97[/tex]

Step-by-step explanation:

From the question  we are told that

 The margin of error is  [tex]E = 1.25[/tex]

   The  standard deviation is  [tex]s = 7.5[/tex]

Given that the confidence level is  90% then the level of significance is mathematically represented as

             [tex]\alpha = 100 - 90[/tex]  

             [tex]\alpha =10\%[/tex]  

             [tex]\alpha =0.10[/tex]

Next we obtain the critical value of [tex]\frac{\alpha }{2}[/tex] from the normal distribution table  

    The value is  [tex]Z_{\frac{ \alpha }{2} } = 1.645[/tex]

   The  minimum sample size is mathematically evaluated as

         [tex]n = \frac{Z_{\frac{\alpha }{2} * s^2 }}{E^2 }[/tex]

=>        [tex]n = \frac{1.645^2 * 7.5^2 }{1.25^2 }[/tex]

=>        [tex]n =97[/tex]


Related Questions

Solve the system of equations.

6x−y=−14
2x−3y=6

whats the answer please C:

Answers

Answer:

Step-by-step explanation:

Which is the zero of the function f(x)=(x+3) (2x-1)(x+2) ?

Answers

Answer:

x= -3     x = 1/2     x=-2

Step-by-step explanation:

f(x)=(x+3) (2x-1)(x+2)

Set equal to zero

0 =(x+3) (2x-1)(x+2)

Using the zero product property

x+3 =0   2x-1 =0    x+2 =0

x= -3    2x =1       x = -2

x= -3     x = 1/2     x=-2

Find the measure of ZJ, the smallest angle in a triangle
with sides measuring 11, 13, and 19. Round to the
nearest whole degree.
O 30°
O 34°
o 42°
O 47°

Answers

Make A the subject
2bc.cos(A) = b^2 + c^2 - a^2
cos(A) = (b^2 + c^2 - c^2) / (2bc)
cos(A) = (13^2 + 19^2 - 11^2) / (2 x 13 x 19) = 0.827935
A = 34 degrees

Simplify using calculator.. I'm not sure if i am putting it in the calculator right

Answers

Answer: D) 64

You would type in

32^(6/5)

Or you could type in

32^(1.2)

since 6/5 = 1.2

Either way, the final result is 64

what is 5(2x - 2y) - (4x + 3y)

Answers

Answer:

6x - 13y

Step-by-step explanation:

5(2x - 2y) - (4x + 3y)

10x - 10y - 4x - 3y

10x - 4x - 10y - 3y

6x - 13y

Solve the equation using square roots x^2+20=4

Answers

Answer:

Step-by-step explanation:

x^2+20=4 first isolate the variable by subtracting 20 on both sides.

x^2=-16 again isolate the variable but this time you square root both sides.

[tex]\sqrt{x}^2[/tex]=[tex]\sqrt{-16[/tex] then simplify

x= ±4

can you please help ?

Answers

Answer:

69

Step-by-step explanation:

The order of operations is PEMDAS; parentheses, exponents, multiplication and division, and finally addition and subtraction.

We know that x is the first row, and if there are 30 spots in the first row, then x=30. Using this information, all we have to do now is plug in 30 for x and solve.

[tex]\frac{5(x)}{2} -6[/tex]

[tex]\frac{5(30)}{2}-6[/tex]

[tex]\frac{150}{2}-6[/tex]

[tex]75-6[/tex]

[tex]69[/tex]

How far from the base of the house do you need to place a 13-foot ladder so that it exactly reaches the top of a 10-feet wall?

Answers

Answer:

√69 or 8.3 feets

Step-by-step explanation:

Hypotenuse=13

Therefore

13²=x²+10²

x²=169-100

x²=69

x=√69 feets

The distance from the base of the house is  8.3 feet.

What is the pythagoras theorem?

The pythagoras theorem is used to obtain the sides of a right angled triangle.

Given that;

The hypotenues of the triangle is 13-foot

The length of the opposite side is 10 feet

Thus;

13^2 = 10^2 + a^2

a^2 = 13^2  -  10^2

a = √13^2  -  10^2

a = 8.3 feet

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A regression was run to determine if there is a relationship between hours of TV watched per day (x) and number of situps a person can do (y). The results of the regression were:

1. y=a+bx
2. b=-0.669
3. a=27.41
4. r2=0.760384
5. r=-0.872

Use this to predict the number of situps a person who watches 3.5 hours of TV can do. Round to one decimal place.

Answers

Answer: The correct answer is 19 sit ups.

Step-by-step explanation: Given that the regression equation to find a  a relationship between hours of TV watched per day (x) and number of situps a person can do (y) was done.

The result was

y = ax+b

Correlation coefficient = 0.865

To predict the number of situps a person who watches 3 hours of TV

y = -1.23(3)+22.738

= 19.048

Approximately 19 situps.

An evergreen nursery usually sells a certain shrub after 9 years of growth and shaping. The growth rate during those 9 years is approximated by
dh/dt = 1.8t + 3,
where t is the time (in years) and h is the height (in centimeters). The seedlings are 10 centimeters tall when planted (t = 0).
(a) Find the height after t years.
h(t) =
(b) How tall are the shrubs when they are sold?
cm

Answers

Answer:

(a) After t years, the height is

18t² + 3t + 10

(b) The shrubs are847 cm tall when they are sold.

Step-by-step explanation:

Given growth rate

dh/dt = 1.8t + 3

dh = (18t + 3)dt

Integrating this, we have

h = 18t² + 3t + C

When t = 0, h = 10cm

Then

10 = C

So

(a) h = 18t² + 3t + 10

(b) Because they are sold after every 9 years, then at t = 9

h = 18(9)² + 3(9) + 10

= 810 + 27 + 10

= 847 cm

Based on a​ poll, 40​% of adults believe in reincarnation. Assume that 4 adults are randomly​ selected, and find the indicated probability. Complete parts​ (a) through​ (d) below.Required:a. The probability that exactly 3 of the 4 adults believe in reincarnation is? b. The probability that all of the selected adults believe in reincarnation is? c. The probability that at least 3 of the selected adults believe in reincarnation is? d. If 4 adults are randomly​selected, is 3 a significantly high number who believe in​reincarnation?

Answers

Complete Question

The complete question is shown on the first uploaded image

Answer:

a

    [tex]P(3) = 0.154[/tex]

b

    [tex]P(4) = 0.026[/tex]

c

   [tex]P( X \ge 3 ) = 0.18[/tex]

d

   option C is correct

Step-by-step explanation:

From the question we are told that

      The probability of success is  p =  0.4

      The sample size is n=  4

 This adults believe follow a binomial distribution is because there are only two outcome one is an adult  believes in  reincarnation and the second an adult does not believe in reincarnation

  The probability of  failure is mathematically evaluated as

              [tex]q = 1 - p[/tex]

substituting values

             [tex]q = 1 - 0.4[/tex]

             [tex]q = 0.6[/tex]

Considering a  

The  probability that exactly 3 of the selected adults believe in reincarnation is mathematically represented as

       [tex]P(3) = \left n} \atop {}} \right. C_ 3 * p^3 * q^{n-3}[/tex]

substituting values

     [tex]P(3) = \left 4} \atop {}} \right. C_ 3 * (0.40)^3 * (0.60)^{4-3}[/tex]

Here [tex]\left 4} \atop {}} \right.C_3[/tex] means  4  combination 3 . i have calculated this using a calculator and the value is  

           [tex]\left 4} \atop {}} \right.C_3 = 4[/tex]

So

         [tex]P(3) = 4* (0.4)^3 * (0.6)[/tex]

          [tex]P(3) = 0.154[/tex]

Considering b

The probability that all of the selected adults believe in reincarnation is mathematically represented as

        [tex]P(n) = \left n} \atop {}} \right. C_ n * p^n * q^{n-n}[/tex]

substituting values

         [tex]P(4) = \left 4} \atop {}} \right. C_ 4 * (0.40)^4 * (0.60)^{4-4}[/tex]

Here [tex]\left 4} \atop {}} \right.C_3[/tex] means  4  combination  . i have calculated this using a calculator and the value is  [tex]\left 4} \atop {}} \right.C_4 = 1[/tex]

so

          [tex]P(4) = 1* (0.4)^4 * 1[/tex]

=>       [tex]P(4) = 0.026[/tex]

Considering c

the probability that at least 3 of the selected adults believe in reincarnation is mathematically represented as

     [tex]P( X \ge 3 ) = P(3 ) + P(n )[/tex]

substituting values

    [tex]P( X \ge 3 ) = 0.154 + 0.026[/tex]

     [tex]P( X \ge 3 ) = 0.18[/tex]

From the calculation the probability that all the 4 randomly selected persons believe in reincarnation is  [tex]p(4) = 0.026 < 0.05[/tex]

But the the probability of 3 out of the 4 randomly selected person believing in reincarnation is [tex]P(3) = 0.154 \ which \ is \ > 0.05[/tex]

Hence 3 is not a  significantly high number of adults who believe in reincarnation because the probability that 3 or more of the selected adults believe in reincarnation is greater than 0.05.

Look at the chore chart--write a notice and a wonder about the chart. Click on the image to see the chart. Enter ur answer

Answers

Answer:

I noticed that to babysit my cousin was the chore that doled out the most, and I wonder why pet my dog is even a chore. Do they not love their pets?

14. Find the distance between (7,217pi/180 ) and (5,-23pi/36 ) on the polar plane.

Answers

Answer: the distance is  3.49 units

Step-by-step explanation:

There are some ways to find the exact distance, i will calculate the distance in rectangular coordinates.

When we have a point (R, θ) in polar coordinates, we can transform it into rectangular coordinates as:

x = R*cos(θ)

y = R*sin(θ)

Then we have:

(7,217pi/180 )

R = 7

θ = (217/180)*pi

x = 7*cos( (217/180)*pi) = -5.59

y = 7*sin( (217/180)*pi) = -4.21

So this point is (-5.59, -4.21) in rectangular coordinates.

And the other point is  (5,-23pi/36 )

R = 5

θ = -(23/36)*pi

x = 5*cos(  -(23/36)*pi ) = -2.11

y = 5*sin(  -(23/36)*pi ) = -4.53

So this point is (-2.11, - 4.53)

Then the point distance between those points is:

D = I (-2.11, -4.53) - (-5.59, -4.21) I

D = I (-2.11 + 5.59, -4.53 + 4.21) I

D = I (3.48, -0.32) I = √( (3.48)^2 + (-0.32)^2) =  3.49

Can Someone please explain this, please. Tell me how do I start the problem Thanks!

Answers

Answer:

x = 35, y = 15°

Step-by-step explanation:

6. Since ΔRST ≅ ΔXYZ, RT = XZ because of CPCTC which means:

x + 21 = 2x - 14

-x = -35

x = 35

7. Again, since ΔRST ≅ ΔXYZ, ∠R ≅ ∠X because of CPCTC which means:

4y - 10 = 3y + 5

y = 15°

Listed below are numbers of Internet users per 100 people and numbers of scientific award winners per 10 million people for different countries. Construct a​ scatterplot, find the value of the linear correlation coefficient​ r, and find the​ P-value of r. Determine whether there is sufficient evidence to support a claim of linear correlation between the two variables. Use a significance level of α= 0.01.


Internet Users 80.3 78.2 56.4 67.6 77.7 38.6

Award Winners 5.6 9.3 3.2 1.6 10.9 0.1


Required:

a. Construct a scatterplot.

b. Determine the null and alternative hypotheses.

c. The test statistic is:_________

d. The P-value is:_________

Answers

Answer:

There is not sufficient evidence to support a claim of linear correlation between the two variables.

Step-by-step explanation:

(a)

The scatter plot for the provided data is attached below.

(b)

The hypothesis to test significance of linear correlation between the two variables is:

H₀: There is no linear correlation between the two variables, i.e. ρ = 0.

Hₐ: There is a significant linear correlation between the two variables, i.e. ρ ≠ 0.

(c)

Use the Excel function: =CORREL(array1, array2) to compute the correlation coefficient, r.

The correlation coefficient between the number of internet users and the award winners is,

r = 0.786.

The test statistic value is:

[tex]t=r\sqrt{\frac{n-2}{1-r^{2}}}[/tex]

  [tex]=0.786\times\sqrt{\frac{6-2}{1-(0.786)^{2}}}\\\\=2.5427\\\\\approx 2.54[/tex]

Thus, the test statistic is 2.54.

(d)

The degrees of freedom is,

df = n - 2  

  = 6 - 2

  = 4

Compute the p-value as follows:

[tex]p-value=2\cdot P(t_{n-2}<2.54)=2\times 0.032=0.064[/tex]

*Use a t-table.

p-value = 0.064 > α = 0.05

The null hypothesis will not be rejected.

Thus, it can be concluded that there is not sufficient evidence to support a claim of linear correlation between the two variables.

The distance between two cities on a map is 4 centimeters. If the scale is 0.5 cm:1 km, how many kilometers apart are the actual cities?

Answers

Answer:

8 km

Step-by-step explanation:

            1 km

4 cm x -------- = 8 km

           0.5 cm

The actual cities are 8 km apart from each other at the scale 0.5 cm = 1 km.

What is ratio?

Ratio basically compares quantities, that means it shows the value of one quantity with respect to the other quantity.

If a and b are two values, their ratio will be a:b,

Given that,

The distance between two cities on a map = 4 centimeters.

Also,  the scale

0.5 cm = 1 km

To find actual distance between cities, use ratio properly,

0.5 cm = 1 km

1 cm = 2 km

4 cm = 8 km

The distance between the actual cities is 8 km.

To learn more about Ratio on :

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A store has clearance items that have been marked down about 30%. They are having a sale, advertising an additional 55% off clearance items. What percent of the original price do you end up paying

Answers

Answer:

60% discount given in total, so only 40% is paid.

Step-by-step explanation:

Need to be in order Smallest to biggest question.

Want to check if my answers are right.

Answers

Answer:

a49%, 1/2,0.55,3/5

b)0.2,1/4,27%,3/10

c)9/10,95%,0.99,97/100

d)30%,1/3,0.6,2/3

e)0.09,10%,11/100,0.125

Which shapes are quadrilaterals?
1. Scalene right triangle
2. Obtuse scalene triangle
3. Isosceles right triangle
4. Hexagon
5. Pentagon
6. Right trapezoid
7. Venn diagram

Answers

Hey there! I'm happy to help!

A quadrilateral is any polygon (enclosed shape) with four sides. Let's see what each of these shapes are.

Scalene right triangle - the prefix tri- means three  (tricycle, tripod, triple, etc.), and all triangles have three sides, so this is not a quadrilateral.Obtuse scalene triangle - once again a triangle, so not a quadrilateral.Isosceles right triangle - would you look at that, another triangle! Not a quadrilateral.Hexagon - a hexagon is a six-sided polygon (hex=six), so this is not a quadrilateral.Pentagon - a pentagon is a five-sided polygon (pent=five, like Pentatonix!). Not a quadrilateralRight trapezoid - a trapezoid is a quadrilateral with at least one pair of parallel sides!Venn diagram - a Venn diagram is a compare and contrast chart made of two overlapping circles (ZERO sides), so this is not a quadrilateral.

So, the only shape on your list that is a quadrilateral is 6. right trapezoid.

Have a wonderful day! :D

Calculate the surface area of this composite shape.

Answers

Answer:

1284 m^2

Step-by-step explanation:

Front face and back face:

2 * [28 m * 5 m + (22 m - 5 m) * 6 m] = 484 m^2

Left face and right face:

2 * 22 m * 8 m = 352 m^2

Bottom face and top face:

2 * 28 m * 8 m = 448 m^2

total surface area = 484 m^2 + 352 m^2 + 448 m^2 = 1284 m^2

please Factor 12n - 18.

Answers

Answer:

[tex]\large \boxed{6(2n-3)}[/tex]

Step-by-step explanation:

[tex]12n-18[/tex]

Factor out 6 from each term.

[tex]6(2n)+6(-3)[/tex]

Take 6 as a common factor.

[tex]6(2n-3)[/tex]

Answer:

[tex] \boxed{3(4n - 6)}[/tex]

Step-by-step explanation:

[tex] \mathsf{12n - 18}[/tex]

In such expression, the factor which is present in all terms of the expression is taken out as common and each term of the expression should be divided by the common factor to get another factor

Factor out 3 from the expression

[tex] \mathsf{ = 3(4n - 6)}[/tex]

Hope I helped!

Best regards!






[tex] \frac{2}{3} \times \frac{2}{3} \times \frac{2}{3} = what[/tex]



Answer I'll make and mark as brainlist.

Answer Fast.
Post on - 2 Aug 2021 ​

Answers

2^3
——
3^3



............

Assume a bank loan requires an interest payment of $85 per year and a principal payment of $1,000 at the end of the loan's eight-year life. What would be the present value of this loan if it carried a 10% interest rate?

Answers

Answer:

The present value is  [tex]PV = \$ 396,987[/tex]

Step-by-step explanation:

From the question we are told that

   The  interest payment per year is  [tex]C = \$ 85[/tex]

    The principal payment is  [tex]P = \$ 1000[/tex]

     The  duration is  n =  8   years

      The  interest rate is  [tex]r = 10\% = 0.10[/tex]

The present value is  mathematically represented as

      [tex]PV = [ \frac{C}{r} * [1 - \frac{1 }{ (1 +r)^n} ] + \frac{P}{(1 + r)^n} ][/tex]

substituting values

      [tex]PV = [ \frac{85}{0.10} * [1 - \frac{1 }{ (1 +0.10)^8} ] + \frac{1000}{(1 + 0.10)^ 8} ][/tex]

      [tex]PV = \$ 396,987[/tex]

Determine the value of x in the figure. Question 1 options: A) x = 90 B) x = 85 C) x = 45 D) x = 135

Answers

Answer:

A.) x=90°

Step-by-step explanation:

Note:

The triangle shown is an isosceles triangle, which means that it has 2 congruent sides (as shown by the small intersecting lines), and this also means that it has two congruent angles.

We are given an angle measure adjacent to one of the missing angles. These two form supplementary angles, which means that they're sum is equal to 180°, or a straight line. So, to find:

[tex]180=135+y[/tex]

y is the unknown angle. Solve for y:

[tex]180-135=y\\\\y=45[/tex]

y is 45°. Since this and the other angle are congruent, add:

[tex]45+45=90[/tex]

Note:

Triangles angles will always add up to a total of 180°.

To find the missing angle x°, use:

[tex]180=a+b+c[/tex]

These are the angles in a triangle. Substitute any known values and solve:

[tex]180=45+45+x\\\\180=90+x\\\\180-90=x\\\\x=90[/tex]

The missing angle x° is 90°.

:Done

Maite has money in an interest-bearing account. The table shows how much money is in the account at the end of each year.
N
Year Amount
1 $1,000.00
$1,030.00
3 $1,060.90
4 $1,092.73
5 $1,125.51
This situation represents
sequence.
The common
is
At the end of the seventh year, Maite will have $
in the account

Answers

Determining how much money will be in the account of Maite at the end of each year, we use an exponential growth factor, since this is a geometric sequence.

1. This situation represents a geometric  sequence.

A geometric sequence increases by a common exponential growth factor.

2. The common exponential factor is 1.03 (which gives a growth rate of 3% annually).  See how this factor is determined below.

3. At the end of the seventh year, Maite will have $1,194.05 in the account.  See the calculation below.

Data and Calculations:

Year    Amount

1       $1,000.00

2      $1,030.00

3      $1,060.90

4      $1,092.73

5       $1,125.51

6      $1,159.27 ($1,125.51 * 1.03)

7      $1,194.05 ($1,159.27 * 1.03)

The common exponential factor = 1.03 (1 + 0.03)

To obtain the common exponential factor, subtract Year 2 account balance from Year 1 account balance.  Divide the result by Year 1 account balance. This operation can also be carried out with Year 2 and Year 3 balances or Year 4 and Year 5 balances.

To determine how much money will be in the account of Maite at the end of Year 6, using Year 5 as a base = (Year 5 account balance * Exponential Factor)

= $1,159.27 ($1,125.51 * 1.03)

To determine Year 7 account balance, we use Year 6 above as the base

= $1.194.05 ($1,159.27 * 1.03)

Learn more about geometric sequence and exponential growth here: https://brainly.com/question/7154553

Answer:

This situation represents a geometric sequence.

The common ratio is 1.03

At the end of the seventh year, Maite will have $1,194.06 in the account.

Step-by-step explanation:

Plato

Consider these five values a population: 7, 4, 6, 4, and 7. Determine the mean of the population. (Round your answer to 1 decimal place.)

Answers

Answer:

[tex]Mean = 5.6[/tex]

Step-by-step explanation:

Given

[tex]7,4,6,4,7[/tex]

Required

Determine the mean

Mean is calculated as thus;

[tex]Mean = \frac{\sum x}{n}[/tex]

Where n is the number of observation;

In this case;

[tex]n = 5[/tex]

and [tex]\sum x[/tex] is the sum of the observations

The expression becomes

[tex]Mean = \frac{7+4+6+4+7}{5}[/tex]

[tex]Mean = \frac{28}{5}[/tex]

[tex]Mean = 5.6[/tex]

Hence, the mean of the population is 5.6

A lottery exists where balls numbered 1 to "20" are placed in an urn. To​ win, you must match the balls chosen in the correct order. How many possible outcomes are there for this​ game?

Answers

Answer: 1860480

Step-by-step explanation:

Initially, there are 20 balls where 5 must be chosen in order.

The number of possible outcomes may be calculated using the concept of permutations.

The formula for permutations is:

nPr =n!/(n−r)!

where n represents the number of items and r represents the number of items to be selected.

The number of ways of selecting 5 balls in order out of 20 is:

20P5 = 20!/15!

= 1860480

To conclude, there are 1860480 possible outcomes.

A middle school has 470 students. Regina surveys a random sample of 40 students and finds that 28 have cell phones. How many students at the school are likely to have cell phones? A. 132 students B. 188 students C. 329 students D. 338 students Please include ALL work! <3

Answers

Answer:

C. 329

Step-by-step explanation:

So 28 is 70% of 40

so we know that 70% percent of students have phones

70% of 470

329

Thats how I solved it have a great day :)

A hot metal bar is submerged in a large reservoir of water whose temperature is 60°F. The temperature of the bar 20 s after submersion is 120°F. After 1 min submerged, the temperature has cooled to 100°F. (Let y be measured in degrees Fahrenheit, and t be measured in seconds.) (a) Determine the cooling constant k. k = s−1 (b) What is the differential equation satisfied by the temperature y(t)? (Use y for y(t).) y'(t) = (c) What is the formula for y(t)? y(t) = (d) Determine the temperature of the bar at the moment it is submerged. (Round your answer to one decimal place.)

Answers

Answer:

a.  k = -0.01014 s⁻¹

b.  [tex]\mathbf{\dfrac{dy}{dt} = - \dfrac{In(\dfrac{3}{2})}{40}(y-60)}[/tex]

c.  [tex]\mathbf{y(t) = 60+ \dfrac{60 \sqrt{3}}{\sqrt{2}} \ e^{\dfrac{-In(\dfrac{3}{2})\ t}{40}}}[/tex]

d.  y(t) = 130.485°F

Step-by-step explanation:

A hot metal bar is submerged in a large reservoir of water whose temperature is 60°F. The temperature of the bar 20 s after submersion is 120°F. After 1 min submerged, the temperature has cooled to 100°F.

(Let y be measured in degrees Fahrenheit, and t be measured in seconds.)

We are to determine :

a.  Determine the cooling constant k. k = s−1

By applying the new law of cooling

[tex]\dfrac{dT}{dt} = k \Delta T[/tex]

[tex]\dfrac{dT}{dt} = k(T_1-T_2)[/tex]

[tex]\dfrac{dT}{dt} = k (T - 60)[/tex]

Taking the integral.

[tex]\int \dfrac{dT}{T-60} = \int kdt[/tex]

㏑ (T -60) = kt + C

T - 60 = [tex]e^{kt+C}[/tex]

[tex]T = 60+ C_1 e^{kt} ---- (1)[/tex]

After 20 seconds, the temperature of the bar submersion is 120°F

T(20) = 120

From equation (1) ,replace t = 20s and T = 120

[tex]120 = 60 + C_1 e^{20 \ k}[/tex]

[tex]120 - 60 = C_1 e^{20 \ k}[/tex]

[tex]60 = C_1 e^{20 \ k} --- (2)[/tex]

After 1 min i.e 60 sec , the temperature  = 100

T(60) = 100

From equation (1) ; replace t = 60 s and T = 100

[tex]100 = 60 + c_1 e^{60 \ t}[/tex]

[tex]100 - 60 =c_1 e^{60 \ t}[/tex]

[tex]40 =c_1 e^{60 \ t} --- (3)[/tex]

Dividing equation (2) by (3) , we have:

[tex]\dfrac{60}{40} = \dfrac{C_1e^{20 \ k } }{C_1 e^{60 \ k}}[/tex]

[tex]\dfrac{3}{2} = e^{-40 \ k}[/tex]

[tex]-40 \ k = In (\dfrac{3}{2})[/tex]

- 40 k = 0.4054651

[tex]k = - \dfrac{0.4054651}{ 40}[/tex]

k = -0.01014 s⁻¹

 

b. What is the differential equation satisfied by the temperature y(t)?

Recall that :

[tex]\dfrac{dT}{dt} = k \Delta T[/tex]

[tex]\dfrac{dT}{dt} = \dfrac{- In (\dfrac{3}{2})}{40}(T-60)[/tex]

Since y is the temperature of the body , then :

[tex]\mathbf{\dfrac{dy}{dt} = - \dfrac{In(\dfrac{3}{2})}{40}(y-60)}[/tex]

(c) What is the formula for y(t)?

From equation (1) ;

where;

[tex]T = 60+ C_1 e^{kt} ---- (1)[/tex]

Let y be measured in degrees Fahrenheit

[tex]y(t) = 60 + C_1 e^{-\dfrac{In (\dfrac{3}{2})}{40}t}[/tex]

From equation (2)

[tex]C_1 = \dfrac{60}{e^{20 \times \dfrac{-In(\dfrac{3}{2})}{40}}}[/tex]

[tex]C_1 = \dfrac{60}{e^{-\dfrac{1}{2} {In(\dfrac{3}{2})}}}[/tex]

[tex]C_1 = \dfrac{60}{e^ {In(\dfrac{3}{2})^{-1/2}}}}[/tex]

[tex]C_1 = \dfrac{60}{\sqrt{\dfrac{2}{3}}}[/tex]

[tex]C_1 = \dfrac{60 \times \sqrt{3}}{\sqrt{2}}}[/tex]

[tex]\mathbf{y(t) = 60+ \dfrac{60 \sqrt{3}}{\sqrt{2}} \ e^{\dfrac{-In(\dfrac{3}{2})\ t}{40}}}[/tex]

(d) Determine the temperature of the bar at the moment it is submerged.

At the moment it is submerged t = 0

[tex]\mathbf{y(0) = 60+ \dfrac{60 \sqrt{3}}{\sqrt{2}} \ e^{\dfrac{-In(\dfrac{3}{2})\ 0}{40}}}[/tex]

[tex]\mathbf{y(t) = 60+ \dfrac{60 \sqrt{3}}{\sqrt{2}} }[/tex]

y(t) = 60 + 70.485

y(t) = 130.485°F

A new fast-food firm predicts that the number of franchises for its products will grow at the rate dn dt = 6 t + 1 where t is the number of years, 0 ≤ t ≤ 15.

Answers

Answer:

The answer is "253"

Step-by-step explanation:

In the given- equation there is mistype error so, the correct equation and its solution can be defined as follows:

Given:

[tex]\bold{\frac{dn}{dt} = 6\sqrt{t+1}}\\[/tex]

[tex]\to dn= 6\sqrt{t+1} \ \ dt.....(a)\\\\[/tex]

integrate the above value:

[tex]\to \int dn= \int 6\sqrt{t+1} \ \ dt \\\\\to n= \frac{(6\sqrt{t+1} )^{\frac{3}{2}}}{\frac{3}{2}}+c\\\\\to n= \frac{(12\sqrt{t+1} )^{\frac{3}{2}}}{3}+c\\\\[/tex]

When the value of n=1 then t=0

[tex]\to 1= \frac{12(0+1)^{\frac{3}{2}}}{3}+c\\\\ \to 1= \frac{12(1)^{\frac{3}{2}}}{3}+c\\\\\to 1-\frac{12}{3}=c\\\\\to \frac{3-12}{3}=c\\\\\to \frac{-9}{3}=c\\\\\to c=-3\\[/tex]

so the value of  n is:

[tex]\to n= \frac{(12\sqrt{t+1} )^{\frac{3}{2}}}{3}-3\\\\[/tex]

when we put the value t= 15 then,

[tex]\to n= \frac{(12\sqrt{15+1} )^{\frac{3}{2}}}{3}-3\\\\\to n= \frac{(12\sqrt{16} )^{\frac{3}{2}}}{3}-3\\\\\to n= \frac{(12\times 64)}{3}-3\\\\\to n= (4\times 64)-3\\\\\to n= 256-3\\\\\to n= 253[/tex]

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