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solniwko [45]
3 years ago
8

Jessica and Franklin are volunteering to paint one of their community member’s fences for service hours. If Jessica could comple

te the job in 6 hours and Franklin could complete the job in 4.5 hours, how long would it take them to complete the job together, to the nearest minute?
Mathematics
2 answers:
tresset_1 [31]3 years ago
8 0
\frac{1}{t} = \frac{1}{6} + \frac{1}{4.5} = \frac{3+4}{18} = \frac{7}{18} 


t=18/7=2.57 hour =154 min

mezya [45]3 years ago
5 0
2.57 hours approximately
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4- A manufacturing process produces items whose weights are normally distributed. It is known that 22.57% of all the items produ
galben [10]

Answer:

\\ \mu = 118\;grams\;and\;\sigma=30\;grams

Step-by-step explanation:

We need to use z-scores and a standard normal table to find the values that corresponds to the probabilities given, and then to solve a system of equations to find \\ \mu\;and\;\sigma.

<h3>First Case: items from 100 grams to the mean</h3>

For finding probabilities that corresponds to z-scores, we are going to use here a <u>Standard Normal Table </u><u><em>for cumulative probabilities from the mean </em></u><em>(Standard normal table. Cumulative from the mean (0 to Z), 2020, in Wikipedia) </em>that is, the "probability that a statistic is between 0 (the mean) and Z".

A value of a z-score for the probability P(100<x<mean) = 22.57% = 0.2257 corresponds to a value of z-score = 0.6, that is, the value is 0.6 standard deviations from the mean. Since this value is <em>below the mean</em> ("the items produced weigh between 100 grams up to the mean"), then the z-score is negative.

Then

\\ z = -0.6\;and\;z = \frac{x-\mu}{\sigma}

\\ -0.6 = \frac{100-\mu}{\sigma} (1)

<h3>Second Case: items from the mean up to 190 grams</h3>

We can apply the same procedure as before. A value of a z-score for the probability P(mean<x<190) = 49.18% = 0.4918 corresponds to a value of z-score = 2.4, which is positive since it is after the mean.

Then

\\ z =2.4\;and\; z = \frac{x-\mu}{\sigma}

\\ 2.4 = \frac{190-\mu}{\sigma} (2)

<h3>Solving a system of equations for values of the mean and standard deviation</h3>

Having equations (1) and (2), we can form a system of two equations and two unknowns values:

\\ -0.6 = \frac{100-\mu}{\sigma} (1)

\\ 2.4 = \frac{190-\mu}{\sigma} (2)

Rearranging these two equations:

\\ -0.6*\sigma = 100-\mu (1)

\\ 2.4*\sigma = 190-\mu (2)

To solve this system of equations, we can multiply (1) by -1, and them sum the two resulting equation:

\\ 0.6*\sigma = -100+\mu (1)

\\ 2.4*\sigma = 190-\mu (2)

Summing both equations, we obtain the following equation:

\\ 3.0*\sigma = 90

Then

\\ \sigma = \frac{90}{3.0} = 30

To find the value of the mean, we need to substitute the value obtained for the standard deviation in equation (2):

\\ 2.4*30 = 190-\mu (2)

\\ 2.4*30 - 190 = -\mu

\\ -2.4*30 + 190 = \mu

\\ \mu = 118

7 0
3 years ago
The sum of 27 and seven times a number is 125. Find the number.
zysi [14]
The number is 14

Here's the solution:

Let the number be x

According to the question,

27+7x=125

//Subtract 27 from both the sides

7x=125-27

7x=98

//divide both the sides by 7

x=98/7

x=14
9 0
3 years ago
Read 2 more answers
Someone please pass the answers to this
arsen [322]

Answer/Step-by-step explanation:

1. The figure is composed of a triangle and a rectangle.

Area of the triangle = ½*base*height

base = 4 ft

height = 12 - 8 = 4ft

Area of triangle = ½*4*4 = 8 ft²

Area of rectangle = length * width

Length = 8 ft

Width = 4 ft

Area of rectangle = 8*4 = 32 ft²

✔️Area of the figure = 8 + 32 = 40 ft²

2. The figure is composed of a semicircle and a triangle

Area of the semicircle = ½(πr²)

radius (r) = 3 cm

π = 3

Area = ½(3*3²) = 13.5 cm²

Area of triangle = ½*base*height

base = 3*2 = 6 cm

height = 6 cm

Area = ½*6*6 = 6 cm²

✔️Area of the figure = 13.5 + 6 = 19.5 cm²

5 0
2 years ago
Point M is the midpoint of point A and point B. Find the coordinates of point B .
kkurt [141]

Answer:

coordinate of point b is 12,1 by midpoint formula

Step-by-step explanation:

take mp formula and evaluate by putting value it will give you x again same process then it will give you u

8 0
2 years ago
Use this graph of velocity vs. time for two objects to answer the question.
Lynna [10]

Using derivatives, it is found that the correct option is:

A. Object C has an acceleration that is greater than the acceleration for D.

The acceleration is the <u>derivative of the velocity</u>, given by change in velocity divided by change in time, that is:

a = \frac{\Delta_v}{\Delta_t}

In this problem:

  • The change in time for objects C and T is the same.
  • The <u>change in velocity for object C is greater</u>, thus, it has a greater acceleration, and the correct option is:

A. Object C has an acceleration that is greater than the acceleration for D.

A similar problem is given at brainly.com/question/14516604

6 0
2 years ago
Read 2 more answers
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