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4 years ago

A rectangle of perimeter 74 cm is 7cm longer than it is wide. what is the length of each side?

Mathematics

1 answer:

Mumz [18]4 years ago

6 0

I assume that you mean: the length is 7cm more than the width, and the perimeter is 74 cm.

If so, we can write down the following system, where l and w represent, respectively, the length and the width:

$\begin{cases}l=w+7\\2(l+w)=74\end{cases} \iff \begin{cases}l=w+7\\l+w=37\end{cases} \iff \begin{cases}l=w+7\\(w+7)+w=37\end{cases}$

We can easily solve the second equation:

$(w+7)+w=37 \iff 2w+7=37 \iff 2w=30 \iff w=15$

And finally solve for the length:

$l=w+7=15+7=22$

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A flagpole sits on the top of a cliff that is 25 m above sea level. If the angle of elevation from a boat on the water to the to

OLEGan [10]

Answer:

3.2 m

Step-by-step explanation:

Let x be the distance between the cliff and the boat.

Since the cliff is 25 m above sea level and the distance between the boat and the height of the cliff are perpendicular, and the line of sight of the boat to the base of a cliff is 29 , these three form a right-angled triangle with hypotenuse side as the line of sight of the elevation of the boat to the base of the cliff.

So, using trigonometric ratios, tan29° = 25/x

x = 25 m/tan29° = 25 m/0.5543 = 45.1 m

Also, the line of sight of the top of the flagpole, the cliff and the distance between the boat and the cliff form a right-angled triangle with hypotenuse side as the line of sight of the top of the flagpole,

Now, the angle of elevation of the top of the flagpole from the top of the boat is 32°, we now find the angle opposite to x, the distance from the boat to the cliff.

Since it is a right-angled triangle, thus one angle is 90° and the unknown angle is A.

So, 90° + 32° + A = 180° (sum of angles in a triangle)

122° + A = 180°

A = 180° - 122°

A = 58°

Let y be the length of the flagpole. In this same triangle, using the sine rule, with x being the side opposite A and 25 + y being the side opposite the 32° angle, where 25 + y = height of cliff + length of flagpole, then

x/sinA = (25 + y)/sin32°

25 + y = xsin32°/sinA

y = xsin32°/sinA - 25

y = 45.1sin32°/sin58° - 25

y = 45.1 × 0.5299/0.8480 - 25

y = 45.1 × 0.6249 - 25

y =28.183 - 25

y = 3.183

y ≅ 3.2 m to one decimal place

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3 years ago

When David first got a job, his annual income was $20,000. He worked hard and got more experience. After 8 years, he realized th

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Answer:

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x=6 y= 40,000

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The scatter plot that represents this situation is attached.

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3 years ago

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A simple random sample of 90 is drawn from a normally distributed population, and the mean is found to be 138, with a standard d

bagirrra123 [75]

The 90% confidence interval for the population mean of the considered population from the given sample data is given by: Option C: [130.10, 143.90]

<h3>
How to find the confidence interval for population mean from large samples (sample size > 30)?</h3>

Suppose that we have:

Sample size n > 30
Sample mean = $\overline{x}$
Sample standard deviation = s
Population standard deviation = $\sigma$
Level of significance = $\alpha$

Then the confidence interval is obtained as

Case 1: Population standard deviation is known

$\overline{x} \pm Z_{\alpha /2}\dfrac{\sigma}{\sqrt{n}}$

Case 2: Population standard deviation is unknown.

$\overline{x} \pm Z_{\alpha /2}\dfrac{s}{\sqrt{n}}$

For this case, we're given that:

Sample size n = 90 > 30
Sample mean = $\overline{x}$ = 138
Sample standard deviation = s = 34
Level of significance = $\alpha$ = 100% - confidence = 100% - 90% = 10% = 0.1 (converted percent to decimal).

At this level of significance, the critical value of Z is: $Z_{0.1/2}$ = ±1.645

Thus, we get:

$CI = \overline{x} \pm Z_{\alpha /2}\dfrac{s}{\sqrt{n}}\\CI = 138 \pm 1.645\times \dfrac{34}{\sqrt{90}}\\\\CI \approx 138 \pm 5.896\\CI \approx [138 - 5.896, 138 + 5.896]\\CI \approx [132.104, 143.896] \approx [130.10, 143.90]$

Thus, the 90% confidence interval for the population mean of the considered population from the given sample data is given by: Option C: [130.10, 143.90]

Learn more about confidence interval for population mean from large samples here:

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2 years ago

A rectangle of perimeter 74 cm is 7cm longer than it is wide. what is the length of each side?​

A rectangle of perimeter 74 cm is 7cm longer than it is wide. what is the length of each side?