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Delicious77 [7]
3 years ago
14

The figure shows a tree SR and a pole PQ casting shadows of lenghts 30m and 15m respectively .if the length of the pole is 4m ,f

ind the height of the tree.
Mathematics
1 answer:
Salsk061 [2.6K]3 years ago
4 0
15/4=3.75
30/3.75=8
The tree is 8m tall.
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A random sample of 1500 self-employed individuals was chosen and asked about the number of hours they work per week. When the da
bija089 [108]

Answer:

1. Approximately 68% work between 39 and 55 hours; 2. Approximately 47.5%; 3. 16% of self-employed individuals work less than 39 hours per week.

Step-by-step explanation:

We can solve this question using the <em>68-95-99.7 rule</em> which states that, in a normal distribution, approximately 68% (more exactly, 68.27%) of the data are about <em>one standard deviation</em> <em>above</em> and <em>below</em> the population mean, 95% (or more exactly, 95.45%) are<em> two standard deviations</em> <em>above</em> and <em>below</em> the population mean, and finally 99.7% (or more exactly, 99.73%) of the data are <em>three standard deviations above</em> and <em>below</em> the population mean.

We can convert or transform any value given in the question to the equivalent <em>z-score</em> so that we can determine how many standard deviations  from the mean are any of these values. For this, we can use the z-score formula:

\\ z = \frac{x - \mu}{\sigma}

Where

<em>x</em> is the value given to determine how far is from the population mean.

\\ \mu is the <em>population mean</em>, and

\\ \sigma is the <em>population standard deviation</em>.

In this case

\\ \mu = 47\;hours

\\ \sigma = 8\;hours

We need to remember that we can use the <em>standard normal table</em> that has all the probabilities for any <em>z-score</em>, that is, <em>standardized values</em> for any normal distribution.

<h3>Solutions</h3><h3>1. Percent of 68% of the self-employed individuals work</h3>

We need to convert any value given to the equivalent z-score and proceed as we described before. So, for any range of values, we have:

For P(x>55 hours) and P(x<39 hours)

\\ z = \frac{x - \mu}{\sigma}

x = 55:

\\ z = \frac{55 - 47}{8} = 1 (a value <em>above</em> the mean).

x = 39:

\\ z = \frac{39 - 47}{8} = -1 (a value <em>below</em> the mean).

As we can see, from the 68-95-99.7 rule, values between x = 39 and x= 47 represent approximately 68% (or more exactly, 68.27%) of the data because they are one standard deviation above (z = 1) and one standard deviation below the mean (z = -1).

Mathematically, P(39<x<55) = 68.27% (approximately 68%). And, this seems to be the answer to the question, since the sum of P(x>55) and P(x<39) represent the complement probability for P(39<x<55), that is, 1 - 0.6827 = 0.3173 (or 31.73%), and because they are at the extremes of the normal distribution at symmetrically both sides, then, the probability for P(x<39) = (0.3173/2 = 0.1586) and P(x>55) = (0.3173/2 = 0.1586).

For the rest of the values, we have:

P(31<x<63)

For x = 31:

\\ z = \frac{31 - 47}{8} = -2 (below the mean)

For x = 63:

\\ z = \frac{63 - 47}{8} = 2 (above the mean)

Thus, P(31<x<63) (or equivalently, P(-2<z<2)) are between <em>two standard deviations</em> above and below the population mean, so this represents, according to the 68-95-99.7 rule, approximately 95% of the cases.

P(23<x<71)

For x = 23:

\\ z = \frac{23 - 47}{8} = -3 (below the mean)

For x = 71:

\\ z = \frac{71 - 47}{8} = 3 (above the mean)

Thus, P(23<x<71) are between three standard deviations above and below the population mean, and this represents, according to the 68-95-99.7 rule, approximately 99.7% of the cases.

P(39<x<55)

We already confirm that these values are between one standard deviation above and below the mean, so this represents, approximately, 68% of the cases, according to the 68-95-99.7 rule.

P(x>47)

We know that the population's mean is 47 hours, and for any normal distribution, values above and below the mean are 50% of the cases. So, P(x>47) = 50% of the cases.

Therefore, "based on the collected data we can say that approximately 68% of the self-employed work" between 39 and 55 hours.

<h3>2. Percent of self-employed individuals that work between 47 and 63 hours</h3>

Using the 68-95-99.7 rule, we can use the following reasoning: because the value for x = 63 is two standard deviations above the mean and for values of two standard deviations above and below the mean this represents 95%, and we already know that the mean = 47, the values above the mean are only the half of 95% (95/2 = 47.5%).

Then, the percent of self-employed individuals that work between 47 and 63 hours per week is 47.5%.

<h3>3. 16% of self-employed individuals work less than how many hours per week</h3>

We know from the 68-95-99.7 rule that approximately 68% of the cases are between one standard deviation below and above the mean. The complement of the values at both extremes of the normal distribution are one half of the complement below and above the mean. So, the complement of 68% is 1 - 0.68 = 0.32. Then, one half (0.32/2 = 0.16) must be below the mean and the other above the mean, at the extreme sides of the normal distribution. Then,  those values for P(z<-1) represents a probability of 16%.

Using the formula for z-scores:

\\ z = \frac{x - \mu}{\sigma}

\\ -1 = \frac{x - 47}{8}

\\ -1 * 8 = x - 47

\\ (-1 * 8) + 47 = x

\\ 39 = x

\\ x = 39

Thus, 16% of self-employed individuals work less than 39 hours per week.

See graphs below.

6 0
3 years ago
If you flip a coin and roll a 6-sided die, what is the probability that you will flip a heads and roll at least a 3?
levacccp [35]
Probability of coin flip = 1/2, probability of die roll = 4/6
1/2 * 4/6 = 1/3 chance
7 0
3 years ago
In a class of 42 students, 18 students are in the Math Club, 5 students
natta225 [31]

Answer:

15 maybe?

Step-by-step explanation:

42 - 14 = 28

18 - 5 = 13

28 - 13 = 15

subtract the 14 because it says it is in neither.

Subtract 5 from 18 because 18 are in math and only 5 are in both math and science.

Subtract 13 from the 28 because those 13 are in math and wont be in science also.

8 0
3 years ago
Read 2 more answers
A school has 100 yards of fabric. The band uses 31 and a third yards of the fabric to make new uniforms. How much fabric does th
notsponge [240]

Answer:

Step-by-step explanation:

68.6

3 0
3 years ago
There are 12chairs in the meeting hall and an odd number of tables.each has the same number of chairs.How many tables are there?
pychu [463]
3 is the only odd factor of 12 (apart from 1) so there are 3 tables that each have 4 chairs around them.

Hope this helps :)
5 0
3 years ago
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