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gogolik [260]
3 years ago
14

A boat traveled 225 miles each way downstream and back. The trip downstream took 9 hours. The trip back took 15 hours. What is t

he speed of the boat in still water? What is the speed of the current?
Mathematics
1 answer:
Karolina [17]3 years ago
5 0

Answer:

Boat = 20 mph

Current = 5 mph

Step-by-step explanation:

If b is the speed of the boat, and c is the speed of the current, then:

b + c = 225 / 9 = 25

b − c = 225 / 15 = 15

Solve the system of equations with elimination.

2b = 40

b = 20

Plug back into either equation to find the speed of the current.

c = 5

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4 0
3 years ago
If you are reading this please help!!!!
Soloha48 [4]

Given:

1.  -3 x^{2}\left(4 x^{3}-7\right)\\$2. $(6 x-5)(2 x+3)$\\3. $(3 x-1)\left(x^{2}+5 x-2\right)$

To find:

The product of the polynomials.

Solution:

1. -3 x^{2}\left(4 x^{3}-7\right) =-3 x^{2}(4 x^{3}) -3 x^{2}(-7)

Multiply the numerical coefficient and add the powers of x.

                          =-12 x^{5}+21 x^{2}

2. (6 x-5)(2 x+3)=6 x(2 x+3)-5(2x+3)

Multiply each term of first polynomial with each term of 2nd polynomial.

Multiply the numerical coefficient and add the powers of x.

                              =12 x^2+18x-10 x-15

                              =12 x^2+8x-15

3. (3 x-1)\left(x^{2}+5 x-2\right)=3 x(x^{2}+5 x-2)-1(x^{2}+5 x-2)

Multiply each term of first polynomial with each term of 2nd polynomial.

Multiply the numerical coefficient and add the powers of x.

                                      =3x^{3}+15 x^2-6x-x^{2}-5 x+2

Add or subtract like terms together.

                                      =3x^{3}+14 x^2-11x+2

The answer for multiplying polynomials:

1. -12 x^{5}+21 x^{2}

2. \  12 x^2+8x-15

3. \ 3x^{3}+14 x^2-11x+2

3 0
3 years ago
In exercises 21 through 24 is it possible to construct a triangle if the given side lengths? If not explain why.
sattari [20]
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7 0
4 years ago
The graph of a proportional relationship passes through (12,16) and (1,y). find y​
anastassius [24]

Answer:

4/3

Step-by-step explanation:

A proportional relationship is a relationship that crosses through the origin or (0,0). This means the slope of the line can be found by subtracting the points (12,16) and (0,0) in the slope formula.

m = \frac{y_2-y_1}{x_2-x_1} =\frac{16-0}{12-0}= \frac{16}{12}=\frac{4}{3}

So the slope is 4/3 and must be the value between any two points on the line.

This means the function moves from (0,0) to (1, 4/3).

4 0
4 years ago
Andrew plans to retire in 32 years. He plans to invest part of his retirement funds in stocks, so he seeks out information on pa
Debora [2.8K]

Answer:

a) 0.0885 = 8.85% probability that the mean annual return on common stocks over the next 40 years will exceed 13%.

b) 0.4129 = 41.29% probability that the mean return will be less than 8%

Step-by-step explanation:

To solve this question, we need to understand the normal probability distribution and the central limit theorem.

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the z-score of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

Central Limit Theorem

The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean \mu and standard deviation \sigma, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean \mu and standard deviation s = \frac{\sigma}{\sqrt{n}}.

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

Mean 8.7% and standard deviation 20.2%.

This means that \mu = 8.7, \sigma = 20.2

40 years:

This means that n = 40, s = \frac{20.2}{\sqrt{40}}

(a) What is the probability (assuming that the past pattern of variation continues) that the mean annual return on common stocks over the next 40 years will exceed 13%?

This is 1 subtracted by the pvalue of Z when X = 13. So

Z = \frac{X - \mu}{\sigma}

By the Central Limit Theorem

Z = \frac{X - \mu}{s}

Z = \frac{13 - 8.7}{\frac{20.2}{\sqrt{40}}}

Z = 1.35

Z = 1.35 has a pvalue of 0.9115

1 - 0.9115 = 0.0885

0.0885 = 8.85% probability that the mean annual return on common stocks over the next 40 years will exceed 13%.

(b) What is the probability that the mean return will be less than 8%?

This is the pvalue of Z when X = 8. So

Z = \frac{X - \mu}{s}

Z = \frac{8 - 8.7}{\frac{20.2}{\sqrt{40}}}

Z = -0.22

Z = -0.22 has a pvalue of 0.4129

0.4129 = 41.29% probability that the mean return will be less than 8%

8 0
3 years ago
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