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3 years ago

15

Samantha deposit 300 in an account that earns an annual interest rate of 2.5 after nine months she computes the simple interest.

What mistakes did Samantha make?

1 answer:

antiseptic1488 [7]3 years ago

4 0

Answer:

She is doing a mistake of calculating interest after 9 months in place of after 12 months.

Step-by-step explanation:

Samantha deposit $300 in an account that earns an annual interest rate of 2.5%.

Now, Samantha after nine months of deposit computes the simple interest.

She is doing a mistake of calculating interest after 9 months in place of after 12 months.

The calculation of interest should be on a yearly basis (i.e. 12 months) as the interest rate is 2.5% per year. (Answer)

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3 years ago

I'm really not sure how to go about solving this algebraic equation, please help! .513 = (2x)^2 / (.05-x)

LiRa [457]

Let's set it up like this:
$0.513=\frac{\left(2x\right)^2}{\left(0.05-x\right)}$
Multiply both sides by $0.05-x$
$0.513\left(0.05-x\right)=\frac{\left(2x\right)^2}{0.05-x}\left(0.05-x\right)$
$0.513\left(0.05-x\right)=4x^2$
We are then going to use the distributive property. Since we also know that the opposite of an number that is squared is the square root, we can also apply that. We would be left with something like this:
$x=-\frac{0.513+\sqrt{0.673569}}{8},\:x=\frac{\sqrt{0.673569}-0.513}{8}$
The variable $x$ can be both positive or negative.
We have found successfully our answer.

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4 0

3 years ago

Lagrange multipliers have a definite meaning in load balancing for electric network problems. Consider the generators that can o

Ivahew [28]

Answer:

The load balance $(x_1,x_2,x_3)=(545.5,272.7,181.8)$ Mw minimizes the total cost

Step-by-step explanation:

<u>Optimizing With Lagrange Multipliers</u>

When a multivariable function f is to be maximized or minimized, the Lagrange multipliers method is a pretty common and easy tool to apply when the restrictions are in the form of equalities.

Consider three generators that can output xi megawatts, with i ranging from 1 to 3. The set of unknown variables is x1, x2, x3.

The cost of each generator is given by the formula

$\displaystyle C_i=3x_i+\frac{i}{40}x_i^2$

It means the cost for each generator is expanded as

$\displaystyle C_1=3x_1+\frac{1}{40}x_1^2$

$\displaystyle C_2=3x_2+\frac{2}{40}x_2^2$

$\displaystyle C_3=3x_3+\frac{3}{40}x_3^2$

The total cost of production is

$\displaystyle C(x_1,x_2,x_3)=3x_1+\frac{1}{40}x_1^2+3x_2+\frac{2}{40}x_2^2+3x_3+\frac{3}{40}x_3^2$

Simplifying and rearranging, we have the objective function to minimize:

$\displaystyle C(x_1,x_2,x_3)=3(x_1+x_2+x_3)+\frac{1}{40}(x_1^2+2x_2^2+3x_3^2)$

The restriction can be modeled as a function g(x)=0:

$g: x_1+x_2+x_3=1000$

Or

$g(x_1,x_2,x_3)= x_1+x_2+x_3-1000$

We now construct the auxiliary function

$f(x_1,x_2,x_3)=C(x_1,x_2,x_3)-\lambda g(x_1,x_2,x_3)$

$\displaystyle f(x_1,x_2,x_3)=3(x_1+x_2+x_3)+\frac{1}{40}(x_1^2+2x_2^2+3x_3^2)-\lambda (x_1+x_2+x_3-1000)$

We find all the partial derivatives of f and equate them to 0

$\displaystyle f_{x1}=3+\frac{2}{40}x_1-\lambda=0$

$\displaystyle f_{x2}=3+\frac{4}{40}x_2-\lambda=0$

$\displaystyle f_{x3}=3+\frac{6}{40}x_3-\lambda=0$

$f_\lambda=x_1+x_2+x_3-1000=0$

Solving for \lambda in the three first equations, we have

$\displaystyle \lambda=3+\frac{2}{40}x_1$

$\displaystyle \lambda=3+\frac{4}{40}x_2$

$\displaystyle \lambda=3+\frac{6}{40}x_3$

Equating them, we find:

$x_1=3x_3$

$\displaystyle x_2=\frac{3}{2}x_3$

Replacing into the restriction (or the fourth derivative)

$x_1+x_2+x_3-1000=0$

$\displaystyle 3x_3+\frac{3}{2}x_3+x_3-1000=0$

$\displaystyle \frac{11}{2}x_3=1000$

$x_3=181.8\ MW$

And also

$x_1=545.5\ MW$

$x_2=272.7\ MW$

The load balance $(x_1,x_2,x_3)=(545.5,272.7,181.8)$ Mw minimizes the total cost

5 0

3 years ago

Line t passes through points (10, 4) and (7, 9). Line u is parallel to line t. What is the slope of line u?

Margarita [4]

Answer: 3/5

Step-by-step explanation:

concept to know: the slope of perpendicular line is always opposite reciprocal

----------------------

Step 1. Find the slope of line t

(y2-y1)/(x2-x1)

=(4-9)/(10-7)

=-5/3

-------------------

Step 2. Apply the concept

Opposite reciprocal of (-5/3)=3/5

Hope this helps!! :)

Please let me know if you have any question

7 0

3 years ago