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3 years ago

5

A bag has 5 red marbles, 6 blue marbles and 4 black marbles. What is the probability of picking a blue marble, replacing it, and

then picking another blue marble?
a. one-fifteenth
b. eight-seventy-fifths
c. four-twenty-fifths
d. one-ninth

1 answer:

defon3 years ago

8 0

I did the math and i think it would be A i hope this i right

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Question 4......................

svp [43]

I would be the last answer because the h of hours would be multiply by 5.

8 0

4 years ago

A welder requires 18 hours to do a job. After the welder and an apprentice work on a job for 6 hours, the welder moves to anothe

Dafna1 [17]

Answer:

the apprentice can complete the job in 30 hours by working alone.

Step-by-step explanation:

Given:

Number of hours required to complete a job by welder = 18 hours

Number of hours welder work on job = 6 hours.

Number of hours required by apprentice to complete the job = 14 hours

We need to find Number of hours required to complete a job by apprentice alone.

Solution:

Let Number of hours required to complete a job by apprentice alone be 'a'.

Also let the job completed be = 1

Now we know that ;

Time required on job is equal to sum of Number of hours welder work on job and Number of hours required by apprentice to complete the job.

framing in equation form we get

Time required on job = $6+14 =20\ hrs$

Now we can say that;

each has done a fraction of the work so we will add to two fraction as number of hours of work done by Total number of hours required to do the work to complete 1 job.

so we can frame the equation as;

$\frac{6}{18}+\frac{20}{a}=1$

By reducing the fraction we get;

$\frac{1}{3}+\frac{20}{a}=1$

Now we will make the denominator common to solve the fraction we get;

$\frac{1\times a}{3\times a}+\frac{20\times3}{a\times3}=1\\\\\frac{a}{3a}+\frac{60}{3a}=1$

Now denominators are same so we will solve the numerator we get;

$\frac{a+60}{3a}=1$

Multiplying both side by 3a we get;

$\frac{a+60}{3a}\times3a=1\times 3a\\\\a+60=3a$

Combining the like terms we get;

$3a-a=60\\\\2a=60$

Dividing both side by 2 we get;

$\frac{2a}{2}=\frac{60}{2}\\\\a=30\ hrs$

Hence the apprentice can complete the job in 30 hours by working alone.

4 0

3 years ago

23. A certain type of gasoline is supposed to have a mean octane rating of at least 90. Suppose measurements are taken on of 5 r

Nostrana [21]

Answer:

a) $p_v =P(Z$

b) Since $p_v$ we can reject the null hypothesis at the significance level given. So based on this we can commit type of Error I.

Because Type I error " is the rejection of a true null hypothesis".

c) $P(\bar X >90)=1-P(Z$

$1-P(Z$

d) For this case we need a z score that accumulates 0.02 of the area on the right tail and 0.98 on the left tail and this value is z=2.054

And we can use this formula:

$2.054=\frac{90-89}{\frac{0.8}{\sqrt{n}}}$

And if we solve for n we got:

$n = (\frac{2.054 *0.8}{1})^2=2.7 \approx 3$

Step-by-step explanation:

Previous concepts and data given

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

We can calculate the sample mean and deviation with the following formulas:

$\bar X = \frac{\sum_{i=1}^n X_i}{n}$

$s=\sqrt{\sum_{i=1}^n (X_i -\bar X)^2}{n-1}$

$\bar X=88.96$ represent the sample mean

$s=1.011$ represent the sample standard deviation

n=5 represent the sample selected

$\alpha$ significance level

State the null and alternative hypotheses.

We need to conduct a hypothesis in order to check if the mean is less than 90, the system of hypothesis would be:

Null hypothesis: $\mu \geq 90$

Alternative hypothesis: $\mu < 90$

If we analyze the size for the sample is < 30 and we don't know the population deviation so is better apply a t test to compare the actual mean to the reference value, and the statistic is given by:

$z=\frac{\bar X-\mu_o}{\frac{\sigma}{\sqrt{n}}}$ (1)

z-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".

Calculate the statistic

We can replace in formula (1) the info given like this:

$z=\frac{88.96-90}{\frac{0.8}{\sqrt{5}}}=-2.907$

Part a

P-value

First we need to calculate the degrees of freedom given by:

$df=n-1=5-1 = 4$

Then since is a left tailed test the p value would be:

$p_v =P(Z$

Part b

Since $p_v$ we can reject the null hypothesis at the significance level given. So based on this we can commit type of Error I.

Because Type I error " is the rejection of a true null hypothesis".

Part c

We want this probability:

$P(\bar X$

The best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\frac{\sigma}{\sqrt{n}}}$

If we apply this formula to our probability we got this:

$P(\bar X >90)=1-P(Z$

$1-P(Z$

Part d

For this case we need a z score that accumulates 0.02 of the area on the right tail and 0.98 on the left tail and this value is z=2.054

And we can use this formula:

$2.054=\frac{90-89}{\frac{0.8}{\sqrt{n}}}$

And if we solve for n we got:

$n = (\frac{2.054 *0.8}{1})^2=2.7 \approx 3$

7 0

3 years ago

If f(x) = x^2 — 3x, explain how to find f(—1.8).

gogolik [260]

Answer:

Plug -1.8 into each x so the equation would become (-1.8)^2 - 3(-1.8)

Step-by-step explanation:

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4 years ago

The Longton cheerleaders are trying to raise at least $3000 on their candy sale. If each box of candy sells for $7.50, how many

nalin [4]

The answer is A, because 7.5 times 400 is 3000 so you need at least 400 boxes.

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3 years ago