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Digiron [165]
3 years ago
11

So far this semester, Warren is averaging a score of 72 points on math tests, which is 20% lower than his average last semester.

What was the average of his scores last semester?
Mathematics
2 answers:
ankoles [38]3 years ago
5 0

Answer:

86.4

Step-by-step explanation:

72x.20= 14.4

72+14.4=86.4

I'm pretty sure this is right

ahrayia [7]3 years ago
3 0
86.4
You have to multiply .20 and 72. which equals 14.4. it was 20% lower so u have to add the 14.4 to the 72 which equals 86.4
You might be interested in
Find c1 and c2 such that M2+c1M+c2I2=0, where I2 is the identity 2×2 matrix and 0 is the zero matrix of appropriate dimension.
Katyanochek1 [597]

The question is missing parts. Here is the complete question.

Let M = \left[\begin{array}{cc}6&5\\-1&-4\end{array}\right]. Find c_{1} and c_{2} such that M^{2}+c_{1}M+c_{2}I_{2}=0, where I_{2} is the identity 2x2 matrix and 0 is the zero matrix of appropriate dimension.

Answer: c_{1} = \frac{-16}{10}

             c_{2}=\frac{-214}{10}

Step-by-step explanation: Identity matrix is a sqaure matrix that has 1's along the main diagonal and 0 everywhere else. So, a 2x2 identity matrix is:

\left[\begin{array}{cc}1&0\\0&1\end{array}\right]

M^{2} = \left[\begin{array}{cc}6&5\\-1&-4\end{array}\right]\left[\begin{array}{cc}6&5\\-1&-4\end{array}\right]

M^{2}=\left[\begin{array}{cc}31&10\\-2&15\end{array}\right]

Solving equation:

\left[\begin{array}{cc}31&10\\-2&15\end{array}\right]+c_{1}\left[\begin{array}{cc}6&5\\-1&-4\end{array}\right] +c_{2}\left[\begin{array}{cc}1&0\\0&1\end{array}\right] =\left[\begin{array}{cc}0&0\\0&0\end{array}\right]

Multiplying a matrix and a scalar results in all the terms of the matrix multiplied by the scalar. You can only add matrices of the same dimensions.

So, the equation is:

\left[\begin{array}{cc}31&10\\-2&15\end{array}\right]+\left[\begin{array}{cc}6c_{1}&5c_{1}\\-1c_{1}&-4c_{1}\end{array}\right] +\left[\begin{array}{cc}c_{2}&0\\0&c_{2}\end{array}\right] =\left[\begin{array}{cc}0&0\\0&0\end{array}\right]

And the system of equations is:

6c_{1}+c_{2} = -31\\-4c_{1}+c_{2} = -15

There are several methods to solve this system. One of them is to multiply the second equation to -1 and add both equations:

6c_{1}+c_{2} = -31\\(-1)*-4c_{1}+c_{2} = -15*(-1)

6c_{1}+c_{2} = -31\\4c_{1}-c_{2} = 15

10c_{1} = -16

c_{1} = \frac{-16}{10}

With c_{1}, substitute in one of the equations and find c_{2}:

6c_{1}+c_{2}=-31

c_{2}=-31-6(\frac{-16}{10} )

c_{2}=-31+(\frac{96}{10} )

c_{2}=\frac{-310+96}{10}

c_{2}=\frac{-214}{10}

<u>For the equation, </u>c_{1} = \frac{-16}{10}<u> and </u>c_{2}=\frac{-214}{10}<u />

6 0
3 years ago
PLz help me! We r doing semester finals and i need to get this lesson finished in 2 hours so i can get my grade up!
Leto [7]

Answer:

$84

Step-by-step explanation:

1. If 20% is marked off, then you are selling it for 80%.

2. 455 * 80% = 364

3. Since you are finding the cost markup from 280, then 364-280=84

6 0
2 years ago
-7 x - 2y = -13 <br> x - 2y = 11
VashaNatasha [74]
Well the first one would convert to
-2y= 7x-13 and the second one would be -2y=-x+11 and you solve from there (lmk if you need the steps) but your final answer would be. Y= -7/2x+ 13/2 and y=1/2x - 11/2
8 0
3 years ago
What is the value of n?
andrey2020 [161]

Answer:

N = 17

Step-by-step explanation:

In a parallelogram the opposite angles are congruent, hence

4n - 2 = 2n + 32 ( subtract 2n from both sides )

2n - 2 = 32 ( add 2 to both sides )

2n = 34 ( divide both sides by 2 )

n = 17

4 0
3 years ago
Use substitution to solve the sy<br> 2x+3y = 19<br> x = 2y-1<br> Solve for x and y
svp [43]

Answer: Y=3, X=5

Step-by-step explanation:

2(2y-1) + 3y=19

4y-2+ 3y=19

7y=21

Y=3

Plug in y in the second equals

X=2(3) -1

X=6-1

X=5

Hope this helps!

8 0
3 years ago
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