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-Dominant- [34]
2 years ago
9

A national survey of middle school students asks how many hours of sleep they get on school nights. Which sample ​best​ represen

ts the population?
a.) A group of 941 students in eighth grade in a certain town
b.) A group of 886 students in sixth grade in a certain county
c.) A group of 795 students in seventh grade in different states
d.) A group of 739 students in different middle school grade levels from various states
Mathematics
1 answer:
mariarad [96]2 years ago
5 0

Answer:

D

Step-by-step explanation:

It wouldnt be a single grade being surveyed so we would choose d in additon a and b isnt national since it says 'in a certain town' and 'in a certain county'.

Which leaves you with D.

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Josh can paint a whole room in m hours while Kevin can paint a whole room in n hours. How many parts of the room can they paint
Leona [35]
<h3>Answer: (m+n)/(mn)</h3>

Work Shown:

Josh:

1 room = m hours

1/m room = 1 hour

Kevin:

1 room = n hours

1/n room = 1 hour

We see that the rates for Josh and Kevin are 1/m and 1/n respectively. This is the amount of a room they paint in one hour. Combine the fractions

1/m + 1/n = n/(mn) + m/(mn) = (n+m)/(mn) = (m+n)/(mn)

The expression (m+n)/(mn) represents how much of the room they get painted in 1 hour. This is if they work together and it assumes neither worker slows the other one down.

7 0
3 years ago
Meg and Rosa played a game. The game lasted 35 minutes and ended at 10:20 a.m.
ANEK [815]

Answer:

9:45 am

Step-by-step explanation:

Hope this helps!

7 0
3 years ago
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There are 500 sheet of paper in the pack Hannah bought. She has used 137 sheets already. How many sheets of paper does Hannah ha
Grace [21]
Just work out 500 takeaway 137
5 0
3 years ago
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A ball of radius 15 has a round hole of radius 5 drilled through its center. Find the volume of the resulting solid. Hint: The u
OverLord2011 [107]

Answer:

The volume of the ball with the drilled hole is:

\displaystyle\frac{8000\pi\sqrt{2}}{3}

Step-by-step explanation:

See attached a sketch of the region that is revolved about the y-axis to produce the upper half of the ball. Notice the function y is the equation of a circle centered at the origin with radius 15:

x^2+y^2=15^2\to y=\sqrt{225-x^2}

Then we set the integral for the volume by using shell method:

\displaystyle\int_5^{15}2\pi x\sqrt{225-x^2}dx

That can be solved by substitution:

u=225-x^2\to du=-2xdx

The limits of integration also change:

For x=5: u=225-5^2=200

For x=15: u=225-15^2=0

So the integral becomes:

\displaystyle -\int_{200}^{0}\pi \sqrt{u}du

If we flip the limits we also get rid of the minus in front, and writing the root as an exponent we get:

\displaystyle \int_{0}^{200}\pi u^{1/2}du

Then applying the basic rule we get:

\displaystyle\frac{2\pi}{3}u^{3/2}\Bigg|_0^{200}=\frac{2\pi(200\sqrt{200})}{3}=\frac{400\pi(10)\sqrt{2}}{3}=\frac{4000\pi\sqrt{2}}{3}

Since that is just half of the solid, we multiply by 2 to get the complete volume:

\displaystyle\frac{2\cdot4000\pi\sqrt{2}}{3}

=\displaystyle\frac{8000\pi\sqrt{2}}{3}

5 0
3 years ago
Juanita is the self-employed owner of Juanita's Linens. Her estimated annual earnings are $73,040 and she expects to pay 27% of
adell [148]

Answer:

  $7724

Step-by-step explanation:

Her estimated quarterly income is $73,040/4 = $18,260.

Her estimated tax rate is ...

  27% + 12.4% + 2.9% = 42.3%

This tax rate applied to her estimated earnings gives an estimated quarterly tax of ...

  $18,260 × 0.423 = $7723.98

  ≈ $7724 . . . . . taxes are rounded to the nearest dollar

7 0
3 years ago
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