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2 years ago

What is the area of the circle below, in terms of ?90 metersO 457O 907O 1807O 81007134

Mathematics

1 answer:

defon2 years ago

3 0

Step 1: Write out the formula

$\begin{gathered} \text{Area of a circle = }\pi r^2 \\ \text{where } \\ r=\text{ the radius of the circle} \end{gathered}$

Step 2: Write out the given values and substitute them into the formula

$r=90m$

Therefore,

$\text{ the area of the circle = }\pi(90)^2=\pi\times8100=8100\pi m^2$

Hence, the area in terms of pi is

$8100\pi$

The last choice is the correct answer

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Find the equation of a line that goes through the points (8, -9) and (-4, 15).

Natasha_Volkova [10]

Answer:

y = - 2x + 7

Step-by-step explanation:

The equation of a line in slope- intercept form is

y = mx + c ( m is the slope and c the y- intercept )

Calculate m using the slope formula

m = $\frac{y_{2}-y_{1} }{x_{2}-x_{1} }$

with (x₁, y₁ ) = (8, - 9) and (x₂, y₂ ) = (- 4, 15)

m = $\frac{15+9}{-4-8}$ = $\frac{24}{-12}$ = - 2, thus

y = - 2x + c ← is the partial equation

To find c substitute either of the 2 points into the partial equation

Using (8, - 9), then

- 9 = - 16 + c ⇒ c = - 9 + 16 = 7

y = - 2x + 7 ← equation of line

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3 years ago

This week, we are covering relationships that can be approximated by linear equations. For instance, y = 453x + 3768 represents

lana [24]

Answer:

See explanation below.

Step-by-step explanation:

We assume that the data is given by :

x: 30, 30, 30, 50, 50, 50, 70,70, 70,90,90,90

y: 38, 43, 29, 32, 26, 33, 19, 27, 23, 14, 19, 21.

Where X represent the cost for scholarships in thousands of dollars and y represent the cost of life for an academic semester (The data comes from the web)

We can find the least-squares line appropriate for this data.

For this case we need to calculate the slope with the following formula:

$m=\frac{S_{xy}}{S_{xx}}$

Where:

$S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}{n}$

$S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}$

So we can find the sums like this:

$\sum_{i=1}^n x_i = 30+30+30+50+50+50+70+70+70+90+90+90=720$

$\sum_{i=1}^n y_i =38+43+29+32+26+33+19+27+23+14+19+21=324$

$\sum_{i=1}^n x^2_i =30^2+30^2+30^2+50^2+50^2+50^2+70^2+70^2+70^2+90^2+90^2+90^2=49200$

$\sum_{i=1}^n y^2_i =38^2+43^2+29^2+32^2+26^2+33^2+19^2+27^2+23^2+14^2+19^2+21^2=9540$

$\sum_{i=1}^n x_i y_i =30*38+30*43+30*29+50*32+50*26+50*33+70*19+70*27+70*23+90*14+90*19+90*21=17540$

With these we can find the sums:

$S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}=49200-\frac{720^2}{12}=6000$

$S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}=17540-\frac{720*324}{12}{12}=-1900$

And the slope would be:

$m=-\frac{1900}{6000}=-0.317$

Nowe we can find the means for x and y like this:

$\bar x= \frac{\sum x_i}{n}=\frac{720}{12}=60$

$\bar y= \frac{\sum y_i}{n}=\frac{324}{12}=27$

And we can find the intercept using this:

$b=\bar y -m \bar x=27-(-0.317*60)=46.02$

So the line would be given by:

$y=-0.317 x +46.02$

We have an inverse linear relationship since the slope is negative between the variables of interest.

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4 years ago

A new car is purchased for 20300 dollars. The value of the car depreciates at 9.5% per year. What will the value of the car be,

Iteru [2.4K]

The starting value is 20,300, and the value is decreasing by 9.5% each year.

Because it decreases by 9.5% each year based on the previous amount, we use an exponential decay model.

A decrease by 9.5% corresponds to multiplying by 91.5% each year.

We write . We plug in 11 years for t.

$A(t)=23000(0.915)^{t}\\\\A(11)=23000(0.915)^{11}\\\\A(11)=7671.18$

$7,671.18

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3 years ago

What is the value of n in the equation shown <br> below? <br> 2²×2n=(2

pychu [463]

Answer:

Step-by-step explanation:

$2^2 \times 2n= (2)\\\\\mathrm{Simplify\:}2^2\times\:2n:\quad 8n\\\\\mathrm{Simplify\:}\left(2\right):\quad 2\\\\8n=2\\\\\mathrm{Divide\:both\:sides\:by\:}8\\\\\frac{8n}{8}=\frac{2}{8}\\\\Simplify\\\\n=\frac{1}{4}$

4 0

4 years ago

Which equation does the graph of the systems of equations solve? 2 linear graphs. They intersect at 1,4

Pepsi [2]

Answer:

See below.

Step-by-step explanation:

There is an infinite n umber of systems of equations that has (1, 4) as its solution. Are you given choices? Try x = 1 and y = 4 in each equation of the choices. The set of two equations that are true when those values of x and y are used is the answer.

6 0

3 years ago