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3 years ago

There are 20 boys and 20 girls in a classroom.

Mathematics

1 answer:

Ede4ka [16]3 years ago

7 0

Answer:20

Step-by-step explanation:

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Iq scores are normally distributed with a mean of 100 and a standard deviation of 15.

bearhunter [10]

Mean is $\mu=100$ and a standard deviation is $\sigma =15$ , then the variable $X\sim N(100,15^2)$ .

Use substitution

$Z=\dfrac{X-\mu}{\sigma},\\ \\ Z=\dfrac{X-100}{15}$ .

This substitution gives you that $Z\sim N(0,1)$ .

a. For X=130, $Z=\dfrac{130-100}{15}=2$ and $Pr(X>130)=Pr(Z>2) =0.9772$ (the decimal value is taken from the Standard Normal Distribution Table).

b. For X=90, $Z=\dfrac{90-100}{15}=-\dfrac{2}{3}$ and for X=110, $Z=\dfrac{110-100}{15}=\dfrac{2}{3}$ . Then $Pr(90$ (the decimal value is taken from the Standard Normal Distribution Table).

6 0

2 years ago

2.1(2.3 + 2.1x) = 11.65 + x. Step by step equation please help

DedPeter [7]

Answer:

x=2

Step-by-step explanation:

2.1(2.3 + 2.1x) = 11.65 + x

Distribute

4.83+4.41x=11.65+x

bring 4.83 over (-)

4.41x=6.82+x

bring x over

4.41x-1(x)=6.82

4.41-1=3.41 so

3.41x=6.82

divide 3.41

x=2

3 0

3 years ago

The Ohio Department of Agriculture tested 203 fuel samples across the state in 1999 for accuracy of the reported octane level. F

OlgaM077 [116]

Answer:

The Sample size is 1918.89035

Step-by-step explanation:

Consider the provided information.

It is given that 14 out of 105 samples failed.

Therefore p = 14/105 = 0.13 3... and q=1-0.133=0.867

Samples would be needed to create a 99 percent confidence interval.

Subtract the confidence level from 1, then divide by two.

$\frac{(1 -0.99)}{2}=0.005$

By standard normal table z=2.5758≈2.58

Calculate the sample size as:

$n=\frac{z^2pq}{e^2}$

Where, e is the margin of error,

Substitute the respective values.

$n=\frac{(2.58)^2(0.133)(0.867)}{(0.02)^2}=1918.89$

Hence, the Sample size is 1918.89035

4 0

3 years ago

Kill’em Dead Pest Control needs to set out 5 roach motels per square yard. In a rectangular studio apartment that’s 7 yards by 4

laila [671]

5 roach motels per square yd

A = L * W
A = 7 * 4
A = 21 square yds

so if they set out 5 roach motels per square yd, then they need to set out :
5 * 21 = 105 roach motels <==

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3 years ago

POSSIBLE PC

bixtya [17]

I think it will be The seconds one so B

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2 years ago