All categories

3 years ago

A contractor is building a desk around a 15 x 20 rectangular swimming pool. He is going to build a 2-foot desk around the pool.

Mathematics

1 answer:

Artist 52 [7]3 years ago

3 0

Answer:

$(15 + 2x)(20 + 2x)$

Step-by-step explanation:

Given

$Length= 15$

$Width = 20$

$Deck = x$ --- on both sides

Required

An expression for total area of the pool

Because the deck will be on both sides,

the dimension of the pool will be:

$L = Length + 2 * deck$ --- Length

$L = 15 + 2x$

$W = Width + 2 * deck$ --- Width

$W = 20 + 2x$

The total area of the pool is calculated as:

$Area = Length * Width$

$A = (15 + 2x) * (20 + 2x)$

$A =(15 + 2x)(20 + 2x)$

Hence, the expression is: $(15 + 2x)(20 + 2x)$

You might be interested in

If one side of a square notebook measures 20 cm, what is the area of the front cover of the notebook?

nexus9112 [7]

Answer:

400cm

Step-by-step explanation:

8 0

3 years ago

A rectangle has a perimeter of 36 inches and a width of 10 inches. What is the length of the rectangle?

leonid [27]

Answer:

Step-by-step explanation:

8 0

3 years ago

Expand and simplify <img src="https://tex.z-dn.net/?f=%20%283x-2%29%5E%7B2%7D%20" id="TexFormula1" title=" (3x-2)^{2} " alt=" (3

Rus_ich [418]

You can just 1) multiply the binomial by itself, or you can use 2) the square of a binomial pattern. I'll show it to you both ways.

1) Multiply the binomial by itself.

(3x - 2)^2 = (3x - 2)(3x - 2) =

Multiply every term of the first binomial by every term of the second binomial, then collect like terms. (This is often called using FOIL.)

= 9x^2 - 6x - 6x + 4

= 9x^2 - 12x + 4

2) Use the square of a binomial pattern

The square of a binomial is

(a - b)^2 = a^2 - 2ab - b^2

a^2 is the square of the first term.
b^2 is the square of the second term.
-2ab is the product of the two terms and 2.

You have

(3x - 2)^2,
where the first term is 3x, and the second term is -2

square the first term: 9x^2
square the last term: 4
the product of the terms and 2 is: -12x

Put it all together, and you get

9x^2 - 12x + 4

just like we got above with the other method.

7 0

3 years ago

Triangle GHI is similar to triangle JKL. If JP = 26, MH = 36 and PK = 16 then GM =

mars1129 [50]

Since the two triangles are similar, then the ratio of the corresponding sides is equal. Therefore;
JP/GM=PK/MH
26/GM = 16/36
GM= (26×36)/16
= 58.5

8 0

3 years ago

A study was conducted and two types of engines, A and B, were compared. Fifty experiments were performed using engine A and 75 u

USPshnik [31]

Answer:

a) -6 mpg.

b) 2.77 mpg

c) The 95% confidence interval for the difference of population mean gas mileages for engines A and B and interpret the results, in mpg, is (-8.77, -3.23).

Step-by-step explanation:

To solve this question, we need to understand the central limit theorem, and subtraction of normal variables.

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.

For a proportion p in a sample of size n, the sampling distribution of the sample proportion will be approximately normal with mean $\mu = p$ and standard deviation $s = \sqrt{\frac{p(1-p)}{n}}$

Subtraction between normal variables:

When two normal variables are subtracted, the mean is the difference of the means, while the standard deviation is the square root of the sum of the variances.

Gas mileage A: Mean 36, standard deviation 6, sample of 50:

$\mu_A = 36, s_A = \frac{6}{\sqrt{50}} = 0.8485$

Gas mileage B: Mean 42, standard deviation 8, sample of 50:

$\mu_B = 42, s_B = \frac{8}{\sqrt{50}} = 1.1314$

Distribution of the difference:

Mean:

$\mu = \mu_A - \mu_B = 36 - 42 = -6$

Standard error:

$s = \sqrt{s_A^2+s_B^2} = \sqrt{0.8485^2+1.1314^2} = 1.4142$

A. Find the point estimate.

This is the difference of means, that is, -6 mpg.

B. Find the margin of error

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1 - 0.95}{2} = 0.025$

Now, we have to find z in the Ztable as such z has a pvalue of $1 - \alpha$ .

That is z with a pvalue of $1 - 0.025 = 0.975$ , so Z = 1.96.

Now, find the margin of error M as such

$M = zs = 1.96*1.4142 = 2.77$

The margin of error is of 2.77 mpg

C. Construct the 95% confidence interval for the difference of population mean gas mileages for engines A and B and interpret the results(5 pts)

The lower end of the interval is the sample mean subtracted by M. So it is -6 - 2.77 = -8.77 mpg

The upper end of the interval is the sample mean added to M. So it is -6 + 2.77 = -3.23 mpg

The 95% confidence interval for the difference of population mean gas mileages for engines A and B and interpret the results, in mpg, is (-8.77, -3.23).

8 0

3 years ago