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3 years ago

If the area of a circle is 121π square units, what is its diameter?

2 answers:

5 0

1 ) A = 121 π
A = r² π
r² π = 121 π
r = √ 121 = 11
The diameter: d = 2 r = 2 * 11 = 22 units
2 ) C = 20 π
C = 2 r π
2 r π = 20 π
r = 20 : 2 = 10 units
A = r² π = 10² π = 100 π square units.

Afina-wow [57]3 years ago

4 0

Area of a circle is defined as πr2 and the diameter as 2r. Plugin the value and you can solve problem c. As for problem d, circumference is 2πr, plugin the value and solve the equation.

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3 years ago

Set up the integral that uses the method of disks/washers to find the volume V of the solid obtained by rotating the region boun

Blababa [14]

Answer:

$a)\: \frac{3}{2} \pi$

$b) \:\frac{47}{5} \pi$

Step-by-step explanation:

$y=3\sqrt x,\:\:y=3,\:\:x=0$

a) about the line y = 3

$3\sqrt x=3$ ⇒ $x = 1$ is the intersection point

So,

$V=\int\limits^1_0\pi(3-3\sqrt x)^2\:dx=\pi\int\limits^1_0(9-18\sqrt x+9x)\:dx=\\\\=\pi(9x-12x^{3/2}+9/2x^2)|^1_0=\pi(9-12+9/2)=\frac{3}{2} \pi$

b) about the line x = 5

$y=3\sqrt x$ ⇒ $x=y^2/9$

So,

$V = \int\limits^3_0\pi([5-0]^2-[5-y^2/9]^2)\:dy=\pi\int\limits^3_0(25-25+10y^2/9-y^4/81)\:dy=\\\\=\pi(10y^3/27-y^5/405)|^3_0=\pi(10-3/5)=\frac{47}{5} \pi$

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4 years ago

Toys r us is having a 38% off sale on all backpacks. if a backpack normally costs $22.00, how much will it be on sale?

Fudgin [204]

we know that

$38\%= \frac{38}{100} =0.38$

The price on sale will be equal to

$(1-0.38)*\$22.00=0.62* \$22.00=\$13.64$

therefore

the answer is

$\$13.64$

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Answer:

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