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andrew-mc [135]
3 years ago
7

I don´t understand this: Lin’s father is paying for a $20 meal. a) He has a 15%-off coupon for the meal. How much is the discoun

t? You can use the double number line for this problem.
Mathematics
1 answer:
Naddika [18.5K]3 years ago
7 0

You'll have to set this up as two separate problems. First, we want to take 15% off the original $20 bill. To do this, you're going to multiply 20 by .15, which gives you $3. So, 15% off $20 is $17.

Now, we want to find 7% of the new bill, so we're going to multiply 17 by .07 to get $1.19, and add it to the $17, making the final bill $18.19. You could also multiply $17 by 1.07 to get your final total without the extra step in the middle, but only do that once you're comfortable with the math.

Pls give brainiest

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Statements that are true for a cylinder with radius r and height h.
vampirchik [111]

Answer:

Only the second and third statements are correct:

Doubling <em>r</em> quadruples the volume.

Doubling <em>h</em> doubles the volume.

Step-by-step explanation:

The volume of a cylinder is given by:

\displaystyle V=\pi r^2h

We can go through each statement and examine its validity.

Statement 1)

If the radius is doubled, our new radius is now 2<em>r</em>. Hence, our volume is:

\displaystyle V=\pi (2r)^2h=4\pi r^2h

So, compared to the old volume, the new volume is quadrupled the original volume.

Statement 1 is not correct.

Statement 2)

Using the previous reasonsing, Statement 2 is correct.

Statement 3)

If the height is doubled, our new height is now 2<em>h</em>. Hence, our volume is:

V=\pi r^2(2h)=2\pi r^2h

So, compared to the old volume, the new volume has been doubled.

Statement 3 is correct.

Statement 4)

Statement 4 is not correct using the previous reasonsing.

Statement 5)

Doubling the radius results in 2<em>r</em> and doubling the height results in 2<em>h</em>. Hence, the new volume is:

V=\pi (2r)^2(2h)=\pi (4r^2)(2h)=8\pi r^2h

So, compared to the old volume, the new volume is increased by eight-fold.

Statement 5 is not correct.

7 0
3 years ago
What is the solution of the system? Use elimination. <br> 3x - 4y = 9<br> -3x + 2y = 9
densk [106]
You add two equations together to eliminate a variable. This particular problem is nice, because it's already setup to eliminate X.

3x - 4y = 9
<span>-3x + 2y = 9
</span>
When we add these two together, 3x - 3x cancels each other out, leaving us with 0x, or nothing.

We continue with -4y + 2y (leaves us with -2y) and 9+9 (18).

-2y = 18

18/-2 = -9.

Now we have y = -9, and we can go back into the problems to solve for x.

<span>3x - 4(-9) = 9
</span>
3x + 36 = 9.

3x = -27

x = -9.

Confirm with the final equation:

-3(-9) + 2(-9) = 9
27 - 18 = 9
9 = 9 --- Confirmed.

6 0
3 years ago
Read 2 more answers
At the start of the 20th century,there were about 100,000 tigers in the wild.In 2014 there were about 3,200.What percent did the
Tcecarenko [31]
The population decreased 31.25%
6 0
2 years ago
What is the quadratic regression equation for the data set? ​ ​ ​ <br><br> PLEASEE HELP ME
Soloha48 [4]
You're trying to find constants a_0,a_1,a_2 such that \hat y=a_0+a_1\hat x+a_2{\hat x}^2. Equivalently, you're looking for the least-square solution to the following matrix equation.


\underbrace{\begin{bmatrix}1&6&6^2\\1&3&3^2\\\vdots&\vdots&\vdots\\1&9&9^2\end{bmatrix}}_{\mathbf A}\underbrace{\begin{bmatrix}a_0\\a_1\\a_2\end{bmatrix}}_{\mathbf x}=\underbrace{\begin{bmatrix}100\\110\\\vdots\\70\end{bmatrix}}_{\mathbf b}

To solve \mathbf{Ax}=\mathbf b, multiply both sides by the transpose of \mathbf A, which introduces an invertible square matrix on the LHS.

\mathbf{Ax}=\mathbf b\implies\mathbf A^\top\mathbf{Ax}=\mathbf A^\top\mathbf b\implies\mathbf x=(\mathbf A^\top\mathbf A)^{-1}\mathbf A^\top\mathbf b

Computing this, you'd find that

\mathbf x=\begin{bmatrix}a_0\\a_1\\a_2\end{bmatrix}\approx\begin{bmatrix}121.119\\-3.786\\-0.175\end{bmatrix}

which means the first choice is correct.
8 0
3 years ago
There are 22 rows of seats on a concert hall: 23 seats are in the 1st row, 27 seats on the 2nd row, 31 seats on the 3rd row, and
JulijaS [17]
We can model this situation with an arithmetic series.
we have to find the number of all the seats, so we need to sum up the number of seats in all of the 22 rows.

1st row: 23
2nd row: 27
3rd row: 31
Notice how we are adding 4 each time.

So we have an arithmetic series with a first term of 23 and a common difference of 4.

We need to find the total number of seats. To do this, we use the formula for the sum of an arithmetic series (first n terms):

Sₙ = (n/2)(t₁ + tₙ)

where n is the term numbers, t₁ is the first term, tₙ is the nth term

We want to sum up to 22 terms, so we need to find the 22nd term

Formula for general term of an arithmetic sequence:

tₙ = t₁ + (n-1)d,

where t1 is the first term, n is the term number, d is the common difference. Since first term is 23 and common difference is 4, the general term for this situation is

tₙ = 23 + (n-1)(4)

The 22nd term, which is the 22nd row, is

t₂₂ = 23 + (22-1)(4) = 107

There are 107 seats in the 22nd row.

So we use the sum formula to find the total number of seats:

S₂₂ = (22/2)(23 + 107) = 1430 seats

Total of 1430 seats.
If all the seats are taken, then the total sale profit is

1430 * $29.99 = $42885.70
4 0
3 years ago
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