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finlep [7]
3 years ago
15

A sphere has a radius of r. What is the area of a cross section taken at a distance of 1/2r from the center of the sphere?

Mathematics
1 answer:
OlgaM077 [116]3 years ago
6 0

Answer:

D. ¾ πr²

Step-by-step explanation:

If r is the radius of the sphere, and R is the radius of circular cross section, then:

r² = (½ r)² + R²

r² = ¼ r² + R²

¾ r² = R²

So the area of the circular cross section is:

A = πR²

A = ¾ πr²

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Sergio039 [100]

This is not an integer; an integer is a whole number that can be positive, negative, or zero such as -1, 0, and 1.

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3 years ago
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Which of the following numbers is a Mersenne prime?<br> A: 90<br> B: 27 - 1<br> C: 211 - 1<br> D: 15
My name is Ann [436]

Answer:

  B:  2⁷-1 = 127

Step-by-step explanation:

A Mersenne prime is a prime of the form 2^n -1, where n is also a prime.

Among the answer choices, neither 90=2·3²·5 nor 15=3·5 is prime. Both 2⁷-1 = 127 and 2¹¹-1 = 2047 are of the right form, but 2047 = 23·89 is a composite number.

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3 0
3 years ago
–12.3 – 14.2 <br><br> A. 0.9 <br> B. 26.5 <br> C. –0.9 <br> D. –26.5
IrinaK [193]

Answer:

-26.5

Step-by-step explanation:

-12.3 - 14.2 =

in addition or subtraction, if the signs are alike, u add them and keep the same sign

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3 0
3 years ago
How can you you tell when a pattern shows counting on by tens
astraxan [27]
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3 years ago
How to solve (x-10)(x + 10)
alexandr402 [8]

Answer:

x² - 100

Step-by-step explanation:

Use the FOIL method. The FOIL method is the way in which you multiply the terms:

FOIL stands for First, Outside, Inside, Last. Multiply:

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Outside:

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Inside:

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Last:

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Combine like terms:

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x² - 100 is your answer.

~

6 0
3 years ago
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