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3 years ago

How to use substitution to solve system of equations

Mathematics

1 answer:

svlad2 [7]3 years ago

4 0

Answer: See explanation.

Step-by-step explanation:

Let's assume that you have a System of two equations. You can solve this System using the Substitution Method.

In order to use that method to solve the System of equations, you can follow the steps shown below:

Step 1: You must choose one of the equations of the system and solve for one of the variables. Let's call this new equation "Equation A"

Step 2: Then you must substitute"Equation A" into the other equation.

Step 3: Now you must solve for the other variable in order to find its value.

Step 4: Finally, you need to substitute the value of the variable obtained in the previous step, into the "Equation A" and then evaluate in order to find the value of the other varibale.

(Note: You can also substitute the value of the variable calculated in Step 3 into any original equation and solve for the other variable to find its value).

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Answer:

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Step-by-step explanation:

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3 years ago

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Plzz answer this as soon as possible! The graph shows the number of miles two cars travel.

Solnce55 [7]

The answer is 15

From the graph:
Car A traveled 60 miles in one hour
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3 years ago

GRE Test: The Graduate Record Examination (GRE) is a test required for admission to many US graduate schools. Student’s scores o

Zepler [3.9K]

Answer:

a) $\bar X=144.3$

b) The 95% confidence interval would be given by (138.846;149.754)

c) n=34

d) n=298

e) n=1190

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

We can calculate the sample mean with this formula:

$\bar X = \frac{\sum_{i=1}^n x_i}{n}$

$\bar X=144.3$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=8.8$ represent the population standard deviation

n=10 represent the sample size

a) Find a point estimate of the population mean

We can calculate the sample mean with this formula:

$\bar X = \frac{\sum_{i=1}^n x_i}{n}$

$\bar X=144.3$

b) Construct a 95% confidence interval for the true mean score for this population.

The confidence interval for the mean is given by the following formula:

$\bar X \pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (1)

Since the Confidence is 0.95 or 95%, the value of $\alpha=0.05$ and $\alpha/2 =0.025$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.025,0,1)".And we see that $t_{\alpha/2}=1.96$

Now we have everything in order to replace into formula (1):

$144.3-1.96\frac{8.8}{\sqrt{10}}=138.846$

$144.3+1.96\frac{8.8}{\sqrt{10}}=149.754$

So on this case the 95% confidence interval would be given by (138.846;149.754)

Part c

The margin of error is given by this formula:

$ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (a)

And on this case we have that ME =+20 and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=(\frac{z_{\alpha/2} \sigma}{ME})^2$ (b)

The critical value for 95% of confidence interval now can be founded using the normal distribution. And in excel we can use this formla to find it:"=-NORM.INV(0.025;0;1)", and we got $z_{\alpha/2}=1.960$ , replacing into formula (5) we got:

$n=(\frac{1.960(8.8)}{3})^2 =33.05 \approx 34$

So the answer for this case would be n=34 rounded up to the nearest integer

Part d

$n=(\frac{1.960(8.8)}{1})^2 =297.493 \approx 298$

So the answer for this case would be n=298 rounded up to the nearest integer

Part e

$n=(\frac{1.960(8.8)}{0.5})^2 =1189.97 \approx 1190$

So the answer for this case would be n=1190 rounded up to the nearest integer

7 0

4 years ago

John and Emily are brother and sister. John has as many brothers as sisters, and Emily has twice as many brothers as sisters. Ho

spin [16.1K]

Answer:

4 boys, 3 girls

Step-by-step explanation:

brothers of John ⇒ x

sisters of John ⇒ y

John has as many brothers as sisters:

x = y

brothers of Emily ⇒ x + 1 (Emily have the same amount of brother as John, plus one (John))

sisters of Emily ⇒ y -1 (Emily have the same amount of sister as John, minus one (herself))

Emily has twice as many brothers as sisters:

2 (y-1) = x+ 1

Now we have a system of 2 equations and 2 variables

x=y (I)

2y - 2 = x + 1 (II)

____________

Replace x in equation II

2y - 2 = y + 1

2y - y = 2 + 1

y = 3

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Replace y in equation I

x = y = 3

That mean that John have 3 brothers plus himself, there is 4 boys in the family and John have 3 sister, so there is 3 girls in the family

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4 years ago

Find the volume of the solid :)

Bingel [31]

answer key

78.4

Step-by-step explanation:

Multiply 7 x 4 =28

Then Multiply 28 x 2.8 = 78.4

<em>That's how you get your answer ∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞∞ hope that helps out</em>

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3 years ago