All categories

2 years ago

Work out the circumference of a circle with radius 6.5cm

Mathematics

1 answer:

denis-greek [22]2 years ago

7 0

Answer:

circumference=13π cm (see below if you need π approximated)

Step-by-step explanation:

Hi there!

The formula for the circumference of a circle is given as 2πr, where r is the radius and π is pi

we are given that the radius of the circle is 6.5 cm

substitute what we know into the equation:

circumference=2πr

circumference=2π*6.5

circumference=13π cm

some places will accept the answer as 13π, but others ask to have π substituted, usually as 3.14 or 22/7

if you need π substituted as 3.14, the answer will be 40.82 cm

if you need π substituted as 22/7, the answer will be about 40.86 cm

Hope this helps! :)

You might be interested in

Use the Divergence Theorem to evaluate S F · dS, where F(x, y, z) = z2xi + y3 3 + sin z j + (x2z + y2)k and S is the top half of

GenaCL600 [577]

Close off the hemisphere $S$ by attaching to it the disk $D$ of radius 3 centered at the origin in the plane $z=0$ . By the divergence theorem, we have

$\displaystyle\iint_{S\cup D}\vec F(x,y,z)\cdot\mathrm d\vec S=\iiint_R\mathrm{div}\vec F(x,y,z)\,\mathrm dV$

where $R$ is the interior of the joined surfaces $S\cup D$ .

Compute the divergence of $\vec F$ :

$\mathrm{div}\vec F(x,y,z)=\dfrac{\partial(xz^2)}{\partial x}+\dfrac{\partial\left(\frac{y^3}3+\sin z\right)}{\partial y}+\dfrac{\partial(x^2z+y^2)}{\partial k}=z^2+y^2+x^2$

Compute the integral of the divergence over $R$ . Easily done by converting to cylindrical or spherical coordinates. I'll do the latter:

$\begin{cases}x(\rho,\theta,\varphi)=\rho\cos\theta\sin\varphi\\y(\rho,\theta,\varphi)=\rho\sin\theta\sin\varphi\\z(\rho,\theta,\varphi)=\rho\cos\varphi\end{cases}\implies\begin{cases}x^2+y^2+z^2=\rho^2\\\mathrm dV=\rho^2\sin\varphi\,\mathrm d\rho\,\mathrm d\theta\,\mathrm d\varphi\end{cases}$

So the volume integral is

$\displaystyle\iiint_Rx^2+y^2+z^2\,\mathrm dV=\int_0^{\pi/2}\int_0^{2\pi}\int_0^3\rho^4\sin\varphi\,\mathrm d\rho\,\mathrm d\theta\,\mathrm d\varphi=\frac{486\pi}5$

From this we need to subtract the contribution of

$\displaystyle\iint_D\vec F(x,y,z)\cdot\mathrm d\vec S$

that is, the integral of $\vec F$ over the disk, oriented downward. Since $z=0$ in $D$ , we have

$\vec F(x,y,0)=\dfrac{y^3}3\,\vec\jmath+y^2\,\vec k$

Parameterize $D$ by

$\vec r(u,v)=u\cos v\,\vec\imath+u\sin v\,\vec\jmath$

where $0\le u\le 3$ and $0\le v\le2\pi$ . Take the normal vector to be

$\dfrac{\partial\vec r}{\partial v}\times\dfrac{\partial\vec r}{\partial u}=-u\,\vec k$

Then taking the dot product of $\vec F$ with the normal vector gives

$\vec F(x(u,v),y(u,v),0)\cdot(-u\,\vec k)=-y(u,v)^2u=-u^3\sin^2v$

So the contribution of integrating $\vec F$ over $D$ is

$\displaystyle\int_0^{2\pi}\int_0^3-u^3\sin^2v\,\mathrm du\,\mathrm dv=-\frac{81\pi}4$

and the value of the integral we want is

(integral of divergence of <em>F</em>) - (integral over <em>D</em>) = integral over <em>S</em>

==> 486π/5 - (-81π/4) = 2349π/20

5 0

3 years ago

Where does the energy stored in coal originally come from?

Tanzania [10]

Answer:

C . The sun

plants absorb light which make carbohydrates which makes a part of bodies of animals and plants . When they die this compound in their bodies which later became coal

4 0

2 years ago

the sum of two numbers is 123. when the larger number is added to 5 times the smaller, the sum is 343. find the numbers.

vovikov84 [41]

Create a system of equations
x + y = 123
5x + y = 343

I use substitution
y = 123 - x
5x + 123 - x = 343
4x + 123 = 343
4x = 220
x = 55

Plug in
x + y = 123
55 + y = 123
y = 68

Check
5x + y = 343
5(55) + 68 = 343
275 + 68 = 343
343 = 343

3 0

1 year ago

Read 2 more answers

ebony wants to buy a dvd player and dvds the equation relates the total cost for dvds and dvd player and N dvds is p=20n+200 wha

kupik [55]

____________________________________________________

Answer:

It represents the cost of the DVD player.

____________________________________________________

Step-by-step explanation:

The reason why it represents the cost of the DVD player is because in the question, it doesn't mention anything about buying multiple DVD players. Ebony would need to buy many DVD's, but doesn't need many DVD players because ebony could use one for all of the DVD's. If you noticed in the question, it says "a DVD player," what this means is that Ebony is only going to buy one DVD player, since it's singular (without and s at the end).

The equation is saying that she starts off with buying 1 DVD player for 200 dollars; and, she is buying n (number of DVDs) for 20 dollars each.

This shows that the 200 in the equation in the question represents the cost of the DVD player.

____________________________________________________

3 0

3 years ago

Figure a is a scale image of figure b. what is the value of x? please answer asap!

emmainna [20.7K]

<em>Greetings from Brasil...</em>

According to the statement, one figure is scaled in relation to another, so we can apply similarity to polygons.....

BIG/small = BIG/small

small/BIG = small/BIG

12.5/10 = X/16

10/12.5 = 16/X

12.5/10 = X/16

10X = 12.5 · 16

X = 200/10

8 0

3 years ago