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Veronika [31]
3 years ago
9

It takes leon 13 hours to seal his driveway working by hinself. If michael helps leon, they can seal the driveway in 7 hours. Ho

w long would it take michael to seal yhe drive way alone?
Mathematics
1 answer:
Monica [59]3 years ago
4 0

Answer:

15.1667 hours (15 hours and 10 minutes)

Step-by-step explanation:

Using the concept of "distance = speed * time", we can formulate equations to solve this problem.

Let's call Leon's speed X, Michael's speed Y and the length of the driveway D.

If leon takes 13 hours alone, we can write the equation:

D = X * 13

If Michael helps Leon, we have this equation:

D = (X+Y) * 7

(The total speed is the sum of their speed, as they are working together)

Making the first equation equate the second, we have:

13*X = 7*X + 7*Y

7*Y = 6*X

X = (7/6)*Y

If we use this value of X in the first equation, we have:

D = 13*X = 13*(7/6)*Y = 15.1667*Y

So we have that Michael would take 15.1667 hours (15 hours and 10 minutes) to seal the driveway alone.

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Answer:

32.1% ( depending on question might have to round to 32% )

Step-by-step explanation:

60*52=3210

3210/100= 32.1

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An auto company claims that the fuel efficiency of its sedan has been substantially improved. A consumer advocate organization w
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Answer:

t=\frac{\bar d -0}{\frac{s_d}{\sqrt{n}}}=\frac{0.983 -0}{\frac{1.685}{\sqrt{12}}}=2.021

df=n-1=12-1=11

p_v =P(t_{(11)}>2.021) =0.0342

If we compare the the p value with the significance level provided \alpha=0.1, we see that p_v < \alpha, so then we can reject the null hypothesis. and there is a significant increase in the miles per gallon from 2017 to 2019 at 10% of significance.

Step-by-step explanation:

Previous concepts

A paired t-test is used to compare two population means where you have two samples in  which observations in one sample can be paired with observations in the other sample. For example  if we have Before-and-after observations (This problem) we can use it.  

Let put some notation :

x=test value 2017 , y = test value 2019

x: 28.7 32.1 29.6 30.5 31.9 30.9 32.3 33.1 29.6 30.8 31.1 31.6

y: 31.1 32.4 31.3 33.5 31.7 32.0 31.8 29.9 31.0 32.8 32.7 33.8

Solution to the problem

The system of hypothesis for this case are:

Null hypothesis: \mu_y- \mu_x \leq 0

Alternative hypothesis: \mu_y -\mu_x >0

Because if we have an improvement we expect that the values for 2019 would be higher compared with the values for 2017

The first step is calculate the difference d_i=y_i-x_i and we obtain this:

d: 2.4, 0.3, 1.7,3,-0.2, 1.1, -0.5, -3.2, 1.4, 2, 1.6, 2.2

The second step is calculate the mean difference  

\bar d= \frac{\sum_{i=1}^n d_i}{n}= \frac{11.8}{12}=0.983

The third step would be calculate the standard deviation for the differences, and we got:

s_d =\frac{\sum_{i=1}^n (d_i -\bar d)^2}{n-1} =1.685

We assume that the true difference follows a normal distribution. The 4th step is calculate the statistic given by :

t=\frac{\bar d -0}{\frac{s_d}{\sqrt{n}}}=\frac{0.983 -0}{\frac{1.685}{\sqrt{12}}}=2.021

The next step is calculate the degrees of freedom given by:

df=n-1=12-1=11

Now we can calculate the p value, since we have a right tailed test the p value is given by:

p_v =P(t_{(11)}>2.021) =0.0342

If we compare the the p value with the significance level provided \alpha=0.1, we see that p_v < \alpha, so then we can reject the null hypothesis. and there is a significant increase in the miles per gallon from 2017 to 2019 at 10% of significance.

4 0
3 years ago
what is a correct first step in solving the inequality –4(3 – 5x)≥ –6x 9? –12 – 20x ≤ –6x 9 –12 – 20x ≥ –6x 9 –12 20x ≤ –6x 9 –1
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we have

-4(3-5x) \geq -6x+9

Step 1

Applying the distributive property in the left side ( Multiply the factors on the left side)

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therefore

<u>the answer is</u>

-12+20x\geq -6x+9

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