Adam has $21 to spend on three pencils. After buying them he had $9. How much did each pencil cost?

Mathematics

2 answers:

iragen [17]3 years ago

8 0

Answer:

Every pencil cost 4$ alll of the pencils together are 12$

Step-by-step explanation:

All you had to do is figure out how much money you wasted on buying the three pencils and from that you have gotten 12$ that you wasted and then you have 3 pencils and so then just divide 12 divided by three which equals 4 so that means that 4$ is your answer.

Mice21 [21]3 years ago

6 0

Answer:

Each Pencil Cost 4 Dollars

Step-by-step explanation:

First you can subtract 21 by 9 to get 12 dollars which shows how much he spent.

Second you can divide 12 by 3 to get 4 dollars spent. So he spent 4 dollars on each pencil.

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Which expression shows the results of applying the distributive property to 3 (1/5x- 1/7)

marshall27 [118]

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2 years ago

Read 2 more answers

In an examination of purchasing patterns of shoppers, a sample of 16 shoppers revealed that they spent, on average, $54 per hour

Lesechka [4]

Answer:

$54-1.64\frac{21}{\sqrt{16}}=45.39$

$54 +1.64\frac{21}{\sqrt{16}}=62.61$

So on this case the 90% confidence interval would be given by (45.39;62.61)

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

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".

$\bar X=54$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=21$ represent the sample standard deviation

n=16 represent the sample size

Solution to the problem

The confidence interval for the mean is given by the following formula:

$\bar X \pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (1)

Since the Confidence is 0.90 or 90%, the value of $\alpha=1-0.9=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.05,0,1)".And we see that $z_{\alpha/2}=1.64$