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3 years ago

If the diameter of a circle is 20mm, what is the area of the circle?

Mathematics

1 answer:

Vsevolod [243]3 years ago

3 0

Answer:

314.16 sq mm

Step-by-step explanation:

formula for area of a circle = pi(r^2)

if the diameter is 20mm then the radius is 10 mm

When you plug in pi(10mm^2) you get 314.16 sq mm

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Solve the system of equations y=x^2-3x+4 x+y=4 show all work please!

Debora [2.8K]

Answer:

(0,4)

(2,2)

Step-by-step explanation:

y=x^2-3x+4

x+y=4

the second one can be rewritten as y=4-x

so the system becomes

y=x^2-3x+4

y=4-x

therefore 4-x = x^2-3x+4

that is x^2-2x=0

we can write it as x(x-2)=0 a product is = 0 when one of its factors = 0

so the solutions for x are: x=0 and x-2= 0 that means x=2

to get y you simply use 0 and 2 as value of x for any of the two equations

and you get y=4 and y=2 respectively

6 0

3 years ago

After arranging the terms in descending powers of a variable, select the opposite of the polynomial.

kondaur [170]

Answer: -4n3+12n2+7n-9

Step-by-step explanation: it basically the opposite sign (positive or negative) switched, and the order backwards. hope that helped

6 0

3 years ago

You have a wire that is 20 cm long. You wish to cut it into two pieces. One piece will be bent into the shape of a square. The o

Aleksandr [31]

Answer:

Therefore the circumference of the circle is $=\frac{20\pi}{4+\pi}$

Step-by-step explanation:

Let the side of the square be s

and the radius of the circle be r

The perimeter of the square is = 4s

The circumference of the circle is =2πr

Given that the length of the wire is 20 cm.

According to the problem,

4s + 2πr =20

⇒2s+πr =10

$\Rightarrow s=\frac{10-\pi r}{2}$

The area of the circle is = πr²

The area of the square is = s²

A represent the total area of the square and circle.

A=πr²+s²

Putting the value of s

$A=\pi r^2+ (\frac{10-\pi r}{2})^2$

$\Rightarrow A= \pi r^2+(\frac{10}{2})^2-2.\frac{10}{2}.\frac{\pi r}{2}+ (\frac{\pi r}{2})^2$

$\Rightarrow A=\pi r^2 +25-5 \pi r +\frac{\pi^2r^2}{4}$

$\Rightarrow A=\pi r^2\frac{4+\pi}{4} -5\pi r +25$

For maximum or minimum $\frac{dA}{dr}=0$

Differentiating with respect to r

$\frac{dA}{dr}= \frac{2\pi r(4+\pi)}{4} -5\pi$

Again differentiating with respect to r

$\frac{d^2A}{dr^2}=\frac{2\pi (4+\pi)}{4}$ > 0

For maximum or minimum

$\frac{dA}{dr}=0$

$\Rightarrow \frac{2\pi r(4+\pi)}{4} -5\pi=0$

$\Rightarrow r = \frac{10\pi }{\pi(4+\pi)}$

$\Rightarrow r=\frac{10}{4+\pi}$

$\frac{d^2A}{dr^2}|_{ r=\frac{10}{4+\pi}}=\frac{2\pi (4+\pi)}{4}>0$

Therefore at $r=\frac{10}{4+\pi}$ , A is minimum.

Therefore the circumference of the circle is

$=2 \pi \frac{10}{4+\pi}$

$=\frac{20\pi}{4+\pi}$

4 0

3 years ago

If you know that R' (20)=50 and R''(20)=-4, approximate R'(24)

vladimir1956 [14]

Approximate R' by using a linear approximation: for x close enough to 24, you have

R'(x) ≈ L(x) = R' (20) + R'' (20) (x - 20)

Then

R' (24) ≈ R' (20) + R'' (20) (24 - 20) = -4 + 50 (24 - 20) = 196

4 0

2 years ago

Megan bought a shirt

Maksim231197 [3]

Answer:

$4.84

Step-by-step explanation:

County A: Multiply the price by the sales tax to find out how much money the sales tax will add. Remember to convert percent to decimal!

$75 * 0.0725 = $5.4375

Add the original price and the sales tax.

$75 + $5.4375 = $80.4375

County B: Multiply the price by the sales tax to find out how much money the sales tax will add. Remember to convert percent to decimal!

$70 * 0.08 = $5.6

Add the original price and the sales tax.

$70 + $5.6 = $75.6

Then take the difference.

80.4375 – 75.6 = 4.8375

Round to the nearest hundredth: $4.84

6 0

3 years ago