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3 years ago

9

Ana Completed 40% of her homework assignment How to Assignments contain 30 math problems how many problems does Anna still need

to complete

1 answer:

yulyashka [42]3 years ago

4 0

Answer:

18

Step-by-step explanation:

30*0.4=12

This means 40% of 30 is 12 and Ana has completed 12 problems.

30-12 = 18, so she still needs to do 18 problems.

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2 years ago

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Answer:

a) 0.0668 = 6.68% probability that a domestic airfare is $550 or more

b) 0.1093 = 10.93% probability than a domestic airfare is $250 or less

c) 0.6313 = 63.13% probability that a domestic airfare is between $300 and $500

d) The cost for the 3% highest domestic airfares are $592 and higher.

Step-by-step explanation:

Problems of normally distributed samples are 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.

In this problem, we have that:

$\mu = 385, \sigma = 110$

a. What is the probability that a domestic airfare is $550 or more (to 4 decimals)?

This is 1 subtracted by the pvalue of Z when X = 550. So

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

$Z = \frac{550 - 385}{110}$

$Z = 1.5$

$Z = 1.5$ has a pvalue of 0.9332

1 - 0.9332 = 0.0668

0.0668 = 6.68% probability that a domestic airfare is $550 or more

b. What is the probability than a domestic airfare is $250 or less (to 4 decimals)?

This is the pvalue of Z when X = 250. So

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

$Z = \frac{250 - 385}{110}$

$Z = -1.23$

$Z = -1.23$ has a pvalue of 0.1093

0.1093 = 10.93% probability than a domestic airfare is $250 or less

c. What if the probability that a domestic airfare is between $300 and $500 (to 4 decimals)?

This is the pvalue of Z when X = 500 subtracted by the pvalue of Z when X = 300. So

X = 500

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

$Z = \frac{500 - 385}{110}$

$Z = 1.045$

$Z = 1.045$ has a pvalue of 0.8519

X = 300

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

$Z = \frac{300 - 385}{110}$

$Z = -0.77$

$Z = -0.77$ has a pvalue of 0.2206

0.8519 - 0.2206 = 0.6313

0.6313 = 63.13% probability that a domestic airfare is between $300 and $500

d. What is the cost for the 3% highest domestic airfares?

At least the 97th percentile, so at least X when Z has a pvalue of 0.97. So X when Z = 1.88.

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

$1.88 = \frac{X - 385}{110}$

$X - 385 = 1.88*110$

$X = 592$

The cost for the 3% highest domestic airfares are $592 and higher.

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3 years ago