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Andrew [12]
3 years ago
15

Shawn and Ellie are construction workers. Shawn can complete a concrete job in 4 hours, while Ellie can complete it in 6 hours.

The foreman says that it will take them 5 hours to complete it if they work together. Explain each step in solving this equation, and determine if the foreman is correct or not.
Mathematics
1 answer:
Firlakuza [10]3 years ago
6 0
If I'm right, the foreman said that it would take the average amount of time to complete a job-since 5 hours is the average amount of time that it takes Shawn and Ellie to complete a job.
The work:
6(Ellie)+4(Shawn)=10/2(number of variables)=5 hours. 
Hope I helped!
You might be interested in
You need to solve a system of equations. You decide to use the elimination method. Which of these is not allowed? 2x - 3y = 12
suter [353]

Answer:

A.

Step-by-step explanation:

The Elimination Method is the method for solving a pair of linear equations which reduces one equation to one that has only a single variable.

If the coefficients of one variable are opposites, you add the equations to eliminate a variable, and then solve.

If the coefficients are not opposites, then we multiply one or both equations by a number to create opposite coefficients, and then add the equations to eliminate a variable and solve.

When multiplying the equation by a coefficient, we multiply both sides of the equation (multiplying both sides of the equation by some nonzero number does not change the solution).

So, option B is not allowed (it is not allowed to multiply only one part of the equation)

6 0
2 years ago
A theater group is having a carwash fundraiser. The group can only wash 45 cars with the amount of soap they purchased. Each car
Vesnalui [34]

Answer:

<h2>The domain for this function is c > 0 where c \in Z.</h2>

Step-by-step explanation:

The given function is

f(c)=7c

Where c represents cars. This function models the profits they make.

Now, as you can deduct already, we can define to different domains, the mathematical one and the reasonable one.

The reasonable domain is about all the useful values to the problem. For example, as we are talking about car, they can't wash -5 cars, so negative numbers are excluded. Similarly, they can't wash 6.75 cars, because that would imply an incomplete job.

Therefore, the domain for this function is c > 0 where c \in Z.

(Notice that we specify that the independent valur can only use whole positive numbers only).

5 0
3 years ago
The average annual cost (including tuition, room, board, books and fees) to attend a public college takes nearly a third of the
Crazy boy [7]

Answer:

a) Private Colleges

Sample mean = 42.5 thousand dollars

Standard deviation = S1 = 6.62 thousand dollars.

Public colleges

Sample mean = 22.3 thousand dollars

Standard deviation = 4.34 thousand dollars

b) The difference in sample mean for both cases = 42.5 - 22.3 = 20.2 thousand dollars

The average amount of going to a Private college is 20.2 thousand dollars more than the average cost of going to public colleges

c) 95% confidence interval for a sampling distribution of the difference of the cost of private and public colleges is given as

(15.0, 25.4) thousand dollars.

Step-by-step explanation:

Private colleges.

52.8 43.2 45.0 33.3 44.0 30.6 45.8 37.8 50.5 42.0

Public colleges.

20.3 22.0 28.2 15.6 24.1 28.5 22.8 25.8 18.5 25.6 14.4 21.8

a) Calculate sample mean and standard deviation for both data set.

Mean = (Σx)/N

where N = Sample size

Σx = sum of all variables

Private colleges

Σx = (52.8+43.2+45.0+33.3+44.0+30.6+45.8+37.8+50.5+42.0) = 425

N = 10

Mean = 425/10 = 42.5 thousand dollars

Standard deviation = S1 = √[Σ(x - xbar)²/N]

Σ(x - xbar)² = (52.8-42.5)² + (43.2-42.5)²

+ (45.0-42.5)² + (33.3-42.5)²

+ (44.0-42.5)² + (30.6-42.5)² + (45.8-42.5)² + (37.8-42.5)² + (50.5-42.5)² + (42.0-42.5)² = 438.56

N = 10

Standard deviation = √[Σ(x - xbar)²/N]

Standard deviation = √(438.56/10) = 6.62 thousand dollars

Public colleges

Mean = (Σx)/N

Σx =

(20.3+22.0+28.2+15.6+24.1+28.5+22.8+25.8+18.5+25.6+14.4+21.8) = 267.6

N = 12

Mean = (267.6/12) = 22.3 thousand dollars

Standard deviation = √[Σ(x - xbar)²/N]

[Σ(x - xbar)²

(20.3-22.3)² + (22.0-22.3)² + (28.2-22.3)² + (15.6-22.3)² + (24.1-22.3)² + (28.5-22.3)² + (22.8-22.3)² + (25.8-22.3)² + (18.5- 22.3)² + (25.6-22.3)² +(14.4-22.3)+(21.8-22.3) = 225.96

N = 12

standard deviation = s2 = √(225.96/12) = 4.34 thousand dollars

b) The difference in sample mean for both cases = 42.5 - 22.3 = 20.2 thousand dollars

The average amount of going to a Private college is 20.2 thousand dollars more than the average cost of going to public colleges.

c. Develop a 95% confidence interval of the difference between the annual cost of attending private and pubic colleges.

95% confidence interval, private colleges have a population mean annual cost $ to $ more expensive than public colleges.

To combine the distribution in this manner,

Sample mean of difference = 20.2 thousand dollars

Combined standard deviation of the sampling distribution = √[(S1²/n1) + (S2²/n2)]

= √[(6.62²/10) + (4.34²/12)] = 2.44 thousand dollars

Confidence interval = (Sample mean) ± (Margin of error)

Sample mean = 20.2

Margin of error = (critical value) × (standard deviation of the sampling distribution)

standard deviation of the sampling distribution = 2.44

To obtain the critical value, we need the t-score at a significance level of 5%; α/2 = 0.025

we obtain the degree of freedom too

The degree of freedom, df, is calculated in the attached image.

df = 15

t (0.025, 15) = 2.13145 from the tables

Margin of error = 2.13145 × 2.44 = 5.20

Confidence interval = (Sample mean) ± (Margin of error)

= (20.2 ± 5.2) = (15.0, 25.4)

Hope this Helps!!!

8 0
3 years ago
What is the answer ....?..?
drek231 [11]

Answer:

A

Step-by-step explanation:

hope it helps :)

7 0
2 years ago
Rewrite each expression by factoring out the coefficient of the variable. 4x - 36
Lubov Fominskaja [6]

Answer:

4(x-9)

Step-by-step explanation:

6 0
3 years ago
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