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shusha [124]
3 years ago
13

A merchant sold a pen for $6.90 ,thereby making a profit of 15% on her cost calculate the cost of the pen to the merchant to the

nearest cent
Mathematics
1 answer:
NeTakaya3 years ago
7 0
So you know the merchant made a 15% profit on the pen, so she bought it for a cheaper price. To find the cost of the pen before you have to take the price now, $6.90 and times it by 85%. You do 85% because you subtract the 15% she saved from 100% and you get 85%. So 6.90x.85= 5.865 which rounds to $5.87
You might be interested in
Derrick will need $39,500 in 10 years for college tuition. How much should his parents invest now at 9.5% annual interest, compo
erastova [34]

Answer:

His parents should invest $15,278.16 to reach this goal ⇒ 4th answer

Step-by-step explanation:

* Lets explain how to solve the problem

- Derrick will need $39,500 in 10 years for college tuition

∴ The future amount is $39,500

∴ The time for investment is 10 years

- P is the money his parents invest now at 9.5% annual interest,

 compounded daily

∴ The rate is 9.5% per year compounded daily

- The formula of the compounded interest is:

  A=P(1+\frac{r}{n})^{nt} , where

# A is the future value of money

# P is the value of investment

# r is the rate of interest in decimal

# t is the time of investment

# n is the period of the time

∵ A = $39,500

∵ t = 10

∵ r = 9.5/100 = 0.095

∵ n = 365 ⇒ compounded daily

- Lets use the formula above to find P

∴ 39500=P(1+\frac{0.095}{365})^{365*10}

∴ 39500=p(2.58539)

- Divide both sides by 2.58539

∴ P = $15278.16

∴ His parents should invest $15,278.16 to reach this goal

7 0
3 years ago
3. The curve C with equation y=f(x) is such that, dy/dx = 3x^2 + 4x +k
Andreas93 [3]

a. Given that y = f(x) and f(0) = -2, by the fundamental theorem of calculus we have

\displaystyle \frac{dy}{dx} = 3x^2 + 4x + k \implies y = f(0) + \int_0^x (3t^2+4t+k) \, dt

Evaluate the integral to solve for y :

\displaystyle y = -2 + \int_0^x (3t^2+4t+k) \, dt

\displaystyle y = -2 + (t^3+2t^2+kt)\bigg|_0^x

\displaystyle y = x^3+2x^2+kx - 2

Use the other known value, f(2) = 18, to solve for k :

18 = 2^3 + 2\times2^2+2k - 2 \implies \boxed{k = 2}

Then the curve C has equation

\boxed{y = x^3 + 2x^2 + 2x - 2}

b. Any tangent to the curve C at a point (a, f(a)) has slope equal to the derivative of y at that point:

\dfrac{dy}{dx}\bigg|_{x=a} = 3a^2 + 4a + 2

The slope of the given tangent line y=x-2 is 1. Solve for a :

3a^2 + 4a + 2 = 1 \implies 3a^2 + 4a + 1 = (3a+1)(a+1)=0 \implies a = -\dfrac13 \text{ or }a = -1

so we know there exists a tangent to C with slope 1. When x = -1/3, we have y = f(-1/3) = -67/27; when x = -1, we have y = f(-1) = -3. This means the tangent line must meet C at either (-1/3, -67/27) or (-1, -3).

Decide which of these points is correct:

x - 2 = x^3 + 2x^2 + 2x - 2 \implies x^3 + 2x^2 + x = x(x+1)^2=0 \implies x=0 \text{ or } x = -1

So, the point of contact between the tangent line and C is (-1, -3).

7 0
2 years ago
Samantha has $300 for guitar lessons to learn her favorite song mr. Jones charges $800 per lesson and requires three lessons to
Ne4ueva [31]

Mr.Jones charges $800 per lesson and requires 3 lessons

That means mr Jones will charge Samantha 800x3 = $2400 in total.

Mr. Police charges $62 per lesson and requires 4 lessons,

62x4 = $248 in total.

Since mr. Police charges less than mr.Jones, it would be a better deal for Samantha.

IN CASE YOU WROTE THE QUESTION WRONG AND MR JONES CHARGES $80 PER LESSON

In that case it would be 80x3 = $240 in total

mr jones would charge less now and it would be better deal for Samantha.

5 0
3 years ago
I will give branliest to the first person to answer!
lara31 [8.8K]

Answer:

1: 10x-5

2: 6.5w-3y

3: 15+3n

4: not sure

8 0
3 years ago
A normally distributed random variable with mean 4.5 and standard deviation 7.6 is sampled to get two independent values, X1 and
mr Goodwill [35]

Answer:

Bias for the estimator = -0.56

Mean Square Error for the estimator = 6.6311

Step-by-step explanation:

Given - A normally distributed random variable with mean 4.5 and standard deviation 7.6 is sampled to get two independent values, X1 and X2. The mean is estimated using the formula (3X1 + 4X2)/8.

To find - Determine the bias and the mean squared error for this estimator of the mean.

Proof -

Let us denote

X be a random variable such that X ~ N(mean = 4.5, SD = 7.6)

Now,

An estimate of mean, μ is suggested as

\mu = \frac{3X_{1} + 4X_{2}  }{8}

Now

Bias for the estimator = E(μ bar) - μ

                                    = E( \frac{3X_{1} + 4X_{2}  }{8}) - 4.5

                                    = \frac{3E(X_{1}) + 4E(X_{2})}{8} - 4.5

                                    = \frac{3(4.5) + 4(4.5)}{8} - 4.5

                                    = \frac{13.5 + 18}{8} - 4.5

                                    = \frac{31.5}{8} - 4.5

                                    = 3.9375 - 4.5

                                    = - 0.5625 ≈ -0.56

∴ we get

Bias for the estimator = -0.56

Now,

Mean Square Error for the estimator = E[(μ bar - μ)²]

                                                             = Var(μ bar) + [Bias(μ bar, μ)]²

                                                             = Var( \frac{3X_{1} + 4X_{2}  }{8}) + 0.3136

                                                             = \frac{1}{64} Var( {3X_{1} + 4X_{2}  }) + 0.3136

                                                             = \frac{1}{64} ( [{3Var(X_{1}) + 4Var(X_{2})]  }) + 0.3136

                                                             = \frac{1}{64} [{3(57.76) + 4(57.76)}]  } + 0.3136

                                                             = \frac{1}{64} [7(57.76)}]  } + 0.3136

                                                             = \frac{1}{64} [404.32]  } + 0.3136

                                                             = 6.3175 + 0.3136

                                                              = 6.6311

∴ we get

Mean Square Error for the estimator = 6.6311

6 0
3 years ago
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