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earnstyle [38]
3 years ago
13

Serena bought a total of 135 notebooks and pencils for her students. Each notebook cost $1.75, and each pencil cost $0.35. The t

otal cost of her purchase was $122.85. How many pencils did Serena buy?
Mathematics
1 answer:
notsponge [240]3 years ago
8 0

Answer:

81 pencils is the answer

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David has a garden with dimension 11 feet long x 9 feet wide. he wants to enlarge the garden to an area of 126. How much farther
kipiarov [429]
Length = 11
Width = 9
Area we need = 126
So Area = length * width
126 = 11 * 9
Now.. this is obviously wrong.. they want us to find the correct length..
126 = L * 9
126/9 = L
L = 14
Now since they ask about how much farther you need to extend, take the final and subtract from the original
14 - 11 = 3
Answer is 3.
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X/5 +7=y <br> solve for x <br> pls help:)))))))))))))
alexandr1967 [171]

Answer:

x = 5 y − 35

Step-by-step explanation:

hope that helps

Brainliest if correct?

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3 years ago
1 HOUR TIME LIMIT
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Answer:

Your answer is 1500 foot pounds.

I hope this helps!

Step-by-step explanation:

Edg 2020

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2 years ago
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Can I someone help me answer this?
ikadub [295]
The dependent is the childrens hospital
7 0
3 years ago
A researcher reports survey results by stating that the standard error of the mean is 25 the population standard deviation is 40
bezimeni [28]

Answer:

a) A sample of 256 was used in this survey.

b) 45.14% probability that the point estimate was within ±15 of the population mean

Step-by-step explanation:

This question is solved using the normal probability distribution and the central limit theorem.

Normal probability distribution

When the distribution is normal, we use 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.

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.

a. How large was the sample used in this survey?

We have that s = 25, \sigma = 400. We want to find n, so:

s = \frac{\sigma}{\sqrt{n}}

25 = \frac{400}{\sqrt{n}}

25\sqrt{n} = 400

\sqrt{n} = \frac{400}{25}

\sqrt{n} = 16

(\sqrt{n})^2 = 16^2[tex][tex]n = 256

A sample of 256 was used in this survey.

b. What is the probability that the point estimate was within ±15 of the population mean?

15 is the bounds with want, 25 is the standard error. So

Z = 15/25 = 0.6 has a pvalue of 0.7257

Z = -15/25 = -0.6 has a pvalue of 0.2743

0.7257 - 0.2743 = 0.4514

45.14% probability that the point estimate was within ±15 of the population mean

3 0
3 years ago
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