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2 years ago

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Christy earns $8 an hour for babysitting. She also earns a weekly bonus of $15 for helping children with their child's homework

assignments. The first week, Christy earned $125 for x hours of work. Based on this situation, which statement is true? Show Work!
(A) Christy worked a total of 17 1/2 hours.
(B) Christy worked a total of 17 3/4 hours.
(C) Christy worked a total of 13 1/2 hours.
(D) Christy worked a total of 13 3/4 hours.

1 answer:

kirza4 [7]2 years ago

5 0

A) Christy worked a total of 17 1/2 hours

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Kirsten's work is shown below:

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She needs to move the decimal point, not just add 0's

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2/3 + 1/4 = 11/12

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The probability that a randomly selected student is a girl is 0.52, and the probability that a student is a girl and in an art c

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Answer: The answer is 0.38

Step-by-step explanation:

Well, everything is given, as stated in the question "the probability that a student is a girl and in an art class is 0.20."

It's given that the probability that a student is a girl is 0.52.

However, in the question, it said that it's given a student is a girl.

You have the probability that a student is a girl and in art class, so you need to find what 0.52 was multiplied by which would be the probability of someone being in art class. Knowing this you can do 0.20 / 0.52 to get 0.38.

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2 years ago

According to a Yale program on climate change communication survey, 71% of Americans think global warming is happening.† (a) For

SpyIntel [72]

Answer:

a) 0.2741 = 27.41% probability that at least 13 believe global warming is occurring

b) 0.7611 = 76.11% probability that at least 110 believe global warming is occurring

Step-by-step explanation:

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

$P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}$

In which $C_{n,x}$ is the number of different combinations of x objects from a set of n elements, given by the following formula.

$C_{n,x} = \frac{n!}{x!(n-x)!}$

And p is the probability of X happening.

The expected value of the binomial distribution is:

$E(X) = np$

The standard deviation of the binomial distribution is:

$\sqrt{V(X)} = \sqrt{np(1-p)}$

Normal probability distribution

Problems of normally distributed samples can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore 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 pvalue, we get the probability that the value of the measure is greater than X.

When we are approximating a binomial distribution to a normal one, we have that $\mu = E(X)$ , $\sigma = \sqrt{V(X)}$ .

In this problem, we have that:

$p = 0.71$

(a) For a sample of 16 Americans, what is the probability that at least 13 believe global warming is occurring?

Here $n = 16$ , we want $P(X \geq 13)$ . So

$P(X \geq 13) = P(X = 13) + P(X = 14) + P(X = 15) + P(X = 16)$

In which

$P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}$

$P(X = 13) = C_{16,13}.(0.71)^{13}.(0.29)^{3} = 0.1591$

$P(X = 14) = C_{16,14}.(0.71)^{14}.(0.29)^{2} = 0.0835$

$P(X = 15) = C_{16,15}.(0.71)^{15}.(0.29)^{1} = 0.0273$

$P(X = 16) = C_{16,16}.(0.71)^{16}.(0.29)^{0} = 0.0042$

$P(X \geq 13) = P(X = 13) + P(X = 14) + P(X = 15) + P(X = 16) = 0.1591 + 0.0835 + 0.0273 + 0.0042 = 0.2741$

0.2741 = 27.41% probability that at least 13 believe global warming is occurring

(b) For a sample of 160 Americans, what is the probability that at least 110 believe global warming is occurring?

Now $n = 160$ . So

$\mu = E(X) = np = 160*0.71 = 113.6$

$\sigma = \sqrt{V(X)} = \sqrt{np(1-p)} = \sqrt{160*0.71*0.29} = 5.74$

Using continuity correction, this is $P(X \geq 110 - 0.5) = P(X \geq 109.5)$ , which is 1 subtracted by the pvalue of Z when X = 109.5. So

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

$Z = \frac{109.5 - 113.6}{5.74}$

$Z = -0.71$

$Z = -0.71$ has a pvalue of 0.2389

1 - 0.2389 = 0.7611

0.7611 = 76.11% probability that at least 110 believe global warming is occurring

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2 years ago

Solve the following x/5=10<br>

sergey [27]

Answer:

x = 50

Step-by-step explanation:

x/5 = 10

Multiply both sides of the equation by 5.

5(x/5) = 5(10)

x = 5(10)

x = 50

The value of x is 50.

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