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4 years ago

Ok

Mathematics

1 answer:

Aleks [24]4 years ago

8 0

I think 34 tens + 20 tens is 54 tens.
-Just add 34 + 20
Hope this helps! :)

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The rectangular field at Wilson Middle School is 300 feet long and 175 feet wide. In gym

coldgirl [10]

the total number of feet they jog is 950 feet.

5 0

3 years ago

Student scores on exams given by a certain instructor have mean 74 and standard deviation 14. This instructor is about to give t

Lapatulllka [165]

Answer:

$P(\bar X >80)=P(Z>2.143)=1-P(z$

Step-by-step explanation:

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".

Let X the random variable that represent the Student scores on exams given by a certain instructor, we know that X have the following distribution:

$X \sim N(\mu=74, \sigma=14)$

The sampling distribution for the sample mean is given by:

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

The deduction is explained below we have this:

$E(\bar X)= E(\sum_{i=1}^{n}\frac{x_i}{n})= \sum_{i=1}^n \frac{E(x_i)}{n}= \frac{n\mu}{n}=\mu$

$Var(\bar X)=Var(\sum_{i=1}^{n}\frac{x_i}{n})= \frac{1}{n^2}\sum_{i=1}^n Var(x_i)$

Since the variance for each individual observation is $Var(x_i)=\sigma^2$ then:

$Var(\bar X)=\frac{n \sigma^2}{n^2}=\frac{\sigma}{n}$

And then for this special case:

$\bar X \sim N(74,\frac{14}{\sqrt{25}}=2.8)$

We are interested on this probability:

$P(\bar X >80)$

And we have already found the probability distribution for the sample mean on part a. So on this case we can use the z score formula given by:

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

Applying this we have the following result:

$P(\bar X >80)=P(Z>\frac{80-74}{\frac{14}{\sqrt{25}}})=P(Z>2.143)$

And using the normal standard distribution, Excel or a calculator we find this:

$P(Z>2.143)=1-P(z$

6 0

4 years ago

It is 3 - kilometer hike to river PJ walks for 500 meters. Then he walks another 1,050 meters. How many more kilometers must PJ

Leviafan [203]

Conversion:
3 km - 3000m
0.5 km - 500 m
1.05 km - 1050 m

Solution:
3, 000 m = 500m + 1050m + n
3, 000 m = 1550m + n
n = 3, 000 m - 1550m
n = 1450m

1.45 kilometers must PJ hike to reach the river.

6 0

3 years ago

When calculating interest on your bank account, the

Mariulka [41]

I think the answer is $68.43. $3421.27 x .02 = $68.43

7 0

3 years ago

7r²+9=1 quadratic equation.

dezoksy [38]

7r²+9=1

the equation is contradictory, just to prove

7r² + 9 = 1

7r² + 9 -1 = 0

7r² + 8 = 0

We write the equation in the form of products of

7 * (r² + 8/7) = 0

the product is equal to 0 when one of the factors is zero

7≠0 ∨ (r² + 8/7) = 0
r² ≠ - 8/7
any number squared is not negative.

We proved that none of the factors is not equal to zero , so the right side of the equation is not equal to the left . The equation is contradictory

7 0

3 years ago