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AleksAgata [21]
3 years ago
15

Two times the first number added to the second number is -7

Mathematics
1 answer:
hodyreva [135]3 years ago
8 0
2a+b=-7
5a+b=-13

b=-2a-7
5a-2a-7=-13
3a=-6
a=-2=first number

2(-2)+b=-7
-4+b+-7
b=-3=second
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The diameter of a circle is 6 centimeters. What is the circle's area?<br><br> Use 3.14 for pi
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Step-by-step explanation:

diameter=

2 \times\pi \times r = 6 \\ r =  \frac{6}{2 \times 3.14}  = 0.955 \\ area = \pi \times  {r}^{2}  = 3.14 \times  {0.955}^{2}  \\  =  2.87\:  {cm}^{2}

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3 years ago
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A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 335335 babies were​ born
strojnjashka [21]

Answer:

The 99​% confidence interval estimate of the percentage of girls born is (74.37%, 85.63%).

Usually, 50% of the babies are girls. This confidence interval gives values considerably higher than that, so the method to increase the probability of conceiving a girl appears to be very effective.

Step-by-step explanation:

Confidence Interval for the proportion:

In a sample with a number n of people surveyed with a probability of a success of \pi, and a confidence level of 1-\alpha, we have the following confidence interval of proportions.

\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}

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For this problem, we have that:

n = 335, \pi = \frac{268}{335} = 0.8

99% confidence level

So \alpha = 0.01, z is the value of Z that has a pvalue of 1 - \frac{0.01}{2} = 0.995, so Z = 2.575.

The lower limit of this interval is:

\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.8 - 2.575\sqrt{\frac{0.8*0.2}{335}} = 0.7437

The upper limit of this interval is:

\pi + z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.8 + 2.575\sqrt{\frac{0.8*0.2}{335}} = 0.8563

For the percentage:

Multiplying the proportions by 100.

The 99​% confidence interval estimate of the percentage of girls born is (74.37%, 85.63%).

Usually, 50% of the babies are girls. This confidence interval gives values considerably higher than that, so the method to increase the probability of conceiving a girl appears to be very effective.

7 0
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A moving box has a square base with an area of 324 in². It's height is 24 inches. What is the volume of the moving box?
Roman55 [17]

The volume of the moving box will be 7776 cubic inches,.

<h3>What is the volume of the rectangular prism?</h3>

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V = Base area x height

A moving box has a square base with an area of 324 in².

Its height is 24 inches.

Then the volume of the moving box will be

V = Base area x height

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More about the volume of the prism link is given below.

brainly.com/question/16246207

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Answer:

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we know that

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