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3 years ago

Need help plz ASAP! It’s due tomorrow! I will give branist

Mathematics

1 answer:

damaskus [11]3 years ago

4 0

Study the Problem

What is the cost of the wallpaper (in dollars per square foot)?

Organize the Facts

The wallpaper covers a rectangle 42 ft by 25.5 ft. It costs $771.12 for that area.

Make a Plan

To find dollars per square foot, we need to divide the dollar amount by the area in square feet. The area needs to be computed. It is the area of a rectangle, so can be found by multiplying length and width.

Plan: multiply length and width of the wall to find its area; divide the cost by that area to find dollars per square foot.

Execute the Plan

area = (42 ft)×(25.5 ft) = 1071 ft²

cost/area = $771.12/(1071 ft²) = $0.72/ft²

Examine the Results

The area is on the order of 40×25 = 1000 ft², and the cost is less than $1000, so the cost will be less than $1 per square foot. The answer is in the right ballpark. If we multiply it out, we should get the given cost:

... 0.72×42×25.5 = 771.12 . . . . agrees with given cost.

The cost of the wallpaper is $0.72 per square foot.

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The heights of baby giraffe are normally distributed with a mean of 63.6 inches and a standard deviation of 2.5 inches. If 100 b

ANEK [815]

Answer:

$P(\bar X$

And we can solve this using the following z score formula:

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

And if we use this formula we got:

$z = \frac{63-63.6}{\frac{2.5}{\sqrt{100}}}= -2.4$

So we can find this probability equivalently like this:

$P( Z$

Step-by-step explanation:

Previous concepts

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".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".

Solution to the problem

Let X the random variable that represent the heights of a population, and for this case we know the distribution for X is given by:

$X \sim N(63.6,2.5)$

Where $\mu=63.6$ and $\sigma=2.5$

We select n =100. Since the distribution for X is normal then we know that the distribution for the sample mean $\bar X$ is given by:

$\bar X \sim N(\mu, \frac{\sigma}{\sqrt{n}})$

We want this probability:

$P(\bar X$

And we can solve this using the following z score formula:

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

And if we use this formula we got:

$z = \frac{63-63.6}{\frac{2.5}{\sqrt{100}}}= -2.4$

So we can find this probability equivalently like this:

$P( Z$

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3 years ago

I'm solving systems and I don't understand how to do it pls helpp

kaheart [24]

Answer:

Use the process of elimination. I'll only do one example since you have 4.

Step-by-step explanation:

Let's do the first question.

2x-3y=-11

2x+y=9

Our goal here is to be left with one variable to solve, this way we can use the answer for that variable to find the other. A.K.A only find X to plug into the equation to find Y. To do this, we'll use the process of elimination, in which we need to cancel out a variable.

X seems the easiest here. To cancel 2 (in the top equation), you need to have a -2. And that -2 needs to be the x coefficient in the 2nd equation, in order for us to "cancel" it out. To get -2, you multiply 2 by -1.

-1(2x+y)= -1(9)

Note that whatever you do to one side, you need to do it to both sides! Hence, why I also multiplied 9 by -1. You should now be left with:

-2x -y = -9

Now, we cancel out the positive 2 and -2 from both equations by adding the two equations.

2x-3y= 11

-2x-y=-9

X cancels out, so we're left with -4y=-20. Solve for Y, which is 5.

-4y=-20

y=5

Now that you have the Y value, plug it into any of the two equations to find your X value.

2x-3y=11

2x-3(5)=11

2x-15=11

2x=26

x=13

And voilah! Our Y value is 5, and our X value is 13.

It's pretty simple once you understand what's going on. All that we did was to cancel out one variable (either X or Y) in the two equations so that we're left with only one variable to solve. If we cancel out X, we only need to solve for Y. You do this by manipulating one of the two equations (doesn't matter which one). Once you find either X or Y, all you need to is to plug it into one of the original equations. Then, you'll have both X and Y.

And that my friend, is the process of elimination. Good luck!

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