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S_A_V [24]
2 years ago
10

40

Mathematics
2 answers:
iris [78.8K]2 years ago
7 0
There is a 21/40 chance a yellow crayon will be chosen or 0.525
irina1246 [14]2 years ago
4 0

Answer:

51%

Step-by-step explanation:

You might be interested in
"A manufacturer of automobile batteries claims that the average length of life for its grade A battery is 55 months. Suppose the
STALIN [3.7K]

Answer:

\\ P(z>-2) = 0.97725 or P(x>49) is about 97.725% (or being less precise 97.5% using the <em>empirical rule</em>).

Step-by-step explanation:

We solve this question using the following information:

  1. We are dealing here with <em>normally distributed data</em>, that is "<em>the frequency distribution of the life length data is known to be mound-shaped</em>".
  2. The normal distribution is defined by two parameters: the population mean (\\ \mu) and the population standard deviation (\\ \sigma). In this case, we have that \\ \mu = 55 months, and \\ \sigma = 3 months.
  3. To find the probabilities, we have to use the <em>standard normal distribution</em>, which has \\ \mu = 0 and \\ \sigma = 1. The probabilities for this distribution are collected in the <em>standard normal table</em>, available in Statistics books or on the Internet. We can also use statistics programs to find these probabilities.
  4. For most cases, we need to use the <em>cumulative standard normal table, </em>and for this we have to previously "transform" a raw score (x) into a z-score using the next formula: \\ z = \frac{x - \mu}{\sigma} [1]. A z-score tells us the distance from the mean that a raw score is from it in <em>standard deviations units</em>. If this value is <em>negative</em>, the raw score is <em>below</em> the mean. Conversely, a <em>positive</em> value indicates that it is <em>above</em> the mean.
  5. The <em>cumulative standard normal table </em>is made for positive values of z. Since the normal distribution is <em>symmetrical</em> around the mean, we can find the negative values of z using this formula: \\ P(z [2].

Having all this information, we can solve the question.

<h3>The percentage of the manufacturer's grade A batteries that will last more than 49 months</h3>

<em>First Step: Use formula [1] to find the z-score of the raw score x = 49 months</em>.

\\ z = \frac{49 - 55}{3}

\\ z = \frac{-6}{3}

\\ z = -2

This means that the raw score is represented by a z-score of \\ z = -2, which tells us that it is<em> two standard deviations below</em> the population mean.

<em>Second Step: Consult this value in the cumulative standard normal table for z = 2 and apply the formula [2] to find the corresponding probability.</em>

For a z = 2, the probability is 0.97725.  

Then

\\ P(z

\\ P(z2)

\\ P(z2)

But we <em>are not asked</em> for P(z<-2) but for P(z>-2) = P(x>49). This probability is the <em>complement</em> of the previous result, that is

\\ P(z>-2) = 1 - P(z

\\ P(z>-2) = 1 - 0.02275

\\ P(z>-2) = 0.97725

That is, the "<em>percentage of the manufacturer's grade A batteries will last more than 49 months</em>" is

\\ P(z>-2) = 0.97725 or about 97.725%

A graph below shows this result.

Notice that if we had used the <em>68-95-99.7 rule</em> (also known as the <em>empirical rule</em>), that is, in a normal distribution, the interval between <em>one standard deviation below and above the mean</em> contains, approximately, 68% of the observations; the interval between <em>two standard deviations below and above the mean</em> contains, approximately, 95% of the observations; and the interval between <em>three standard deviations</em> below and above the mean contains, approximately, 99.7% of the observations, we could have concluded that 2.5 % of the manufacturer's grade A batteries will last <em>less</em> than 49 months, and, as a result, 1 - 0.025 = 0.975 or 97.5% will last more than 49 months.

We can conclude that with a less precise answer (but faster) because of the <em>symmetry of the normal distribution</em>, that is, 1 - 0.95 = 0.05. At both extremes we have 0.05/2 = 0.025 or 2.5% and we were asked for P(x>49) = P(z>-2) (see the graph below).

6 0
3 years ago
The center of the circle is at (-2,-7) and its radius is 36.
Vanyuwa [196]
Standard form for circle with radius r and center (h,k) is
(x-h)^2+(y-k)^2=r^2

r=36
center at -2,-7
(x-(-2))^2+(y-(-7))^2=36^2
(x+2)^2+(y+7)^2=1296


firts option
6 0
2 years ago
Please help:<br> In Δ ABC, sin A= 77, sin C= 23, and c =16, find the length of A.
Dafna1 [17]

Answer:

39.9

Step-by-step explanation:

a/sinA = c/sinC

a/sin(77) = 16/sin(23)

a = sin(77) × 16/sin(23)

a = 39.89935764

3 0
2 years ago
A environmental initiative has the goal of saving at least 25 2525 million hectares of rainforest through both planting trees an
Anestetic [448]

Answer:

The possible way for the initiative to accomplish its goal without exceeding its budget is use 12.5 hectares for planting trees and 12.5 hectares by purchasing land.

Step-by-step explanation:

Let the variable <em>X</em> represent the amount of land used for planting trees and <em>Y</em> represent the amount of land purchased.

The goal of the environmental initiative is to save at least 25 million hectares of rain forest.

That is:

<em>X</em> + <em>Y</em> = 25....(i)

Now it is provided that:

  • The cost of planting trees is $ 400 per hectare.
  • The cost of purchasing land is $ 260 per hectare.
  • The initiative has a budget of $8,250 million.

Using the above data it can be said that:

400<em>X</em> + 260<em>Y</em> = 8250....(ii)

Solve equations (i) and (ii) simultaneously.

\ \ \ \ x+y=25]\times 260\\400x+260y=8250\\\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\\\\\Rightarrow\\\\260x+260y=6500\\400x+260y=8250\\(-)\_\_\_\_\_\ (-)\_\_\_\_(-)\_\_\_\\\\\Rightarrow\\\\-140x=-1750\\\\x=\frac{1750}{140}\\\\x=12.5

Then the value of <em>y</em> is:

x+y=25\\y=25-x\\y=25-12.5\\y=12.5

Thus, the possible way for the initiative to accomplish its goal without exceeding its budget is use 12.5 hectares for planting trees and 12.5 hectares for purchasing land.

4 0
3 years ago
Which subtraction expression does the number line model show ​
loris [4]

Answer:

13-+4

Step-by-step explanation:

3 0
3 years ago
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