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Gre4nikov [31]
3 years ago
8

Out of 2,000 random but normally distributed numbers with a mean of 45 and a standard deviation of x, approximately 1,360 number

s are found to be between 40 and 50. What is the value of x? A. 5 B. 10 C. -5 D. 680
Mathematics
1 answer:
lina2011 [118]3 years ago
5 0

Answer:

A. 5

Step-by-step explanation:

It says that the sample is normally distributed, which means it follows the bell curve in terms of spreading.  That means that 68% of the numbers are within two standard deviations, centered on the mean, one standard deviation below, one up.

That's confirmed by the fact that 1,360 numbers (exactly 68% of 2,000) are between 40 and 50.  Since the mean is 45, that gives a spread of ± 1 standard deviation for 68% of the numbers.

One standard deviation goes from 40 to 45, another from 45 to 50.

So, the standard deviation of this sample is 5.

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Estimate the square root to the nearest integer and tenth square root of 8
Sever21 [200]

Answer:

√

8

≈

3

Explanation:

Note that:

2

2

=

4

<

8

<

9

=

3

2

Hence the (positive) square root of  

8

is somewhere between  

2

and  

3

. Since  

8

is much closer to  

9

=

3

2

than  

4

=

2

2

, we can deduce that the closest integer to the square root is  

3

.

We can use this proximity of the square root of  

8

to  

3

to derive an efficient method for finding approximations.

Consider a quadratic with zeros  

3

+

√

8

and  

3

−

√

8

:

(

x

−

3

−

√

8

)

(

x

−

3

+

√

8

)

=

(

x

−

3

)

2

−

8

=

x

2

−

6

x

+

1

From this quadratic, we can define a sequence of integers recursively as follows:

⎧

⎪

⎨

⎪

⎩

a

0

=

0

a

1

=

1

a

n

+

2

=

6

a

n

+

1

−

a

n

The first few terms are:

0

,

1

,

6

,

35

,

204

,

1189

,

6930

,

...

The ratio between successive terms will tend very quickly towards  

3

+

√

8

.

So:

√

8

≈

6930

1189

−

3

=

3363

1189

≈

2.828427

8 0
3 years ago
Which is better? 30 ounces for $2.49 or 40 ounces for 3.32
viva [34]
They're both the same. But 40 ounces for 3.32 would be better
6 0
3 years ago
Read 2 more answers
2.4 Find the coordinates of the figure after reflecting in the x-axis. 1. D(-5, - 4), E(-5, -2), F(-1, -2), G(-1,-4)
posledela

Answer:

see explanation

Step-by-step explanation:

Under a reflection in the x- axis

a point (x, y ) → (x, - y ) , then

D (- 5, - 4 ) → D' (- 5, 4 )

E (- 5, - 2 ) → E' (- 5, 2 )

F (- 1, - 2 ) → F' (- 1, 2 )

G (- 1, - 4 ) → G' (- 1, 4 )

8 0
3 years ago
How many solutions does the nonlinear system of equations graphed below have?
serg [7]

Answer:it’s obvi “C”.

Step-by-step explanation:

8 0
3 years ago
Help please! Math Nation Section 6 Test Yourself Practice Tool.
aalyn [17]

Answer: D)  y=-5(x-5)^2+1125

Step-by-step explanation:

Let x be the number of $2 increases in price and y be the revenue.

By using the given table , lets check all the options

A) y=(x+5)^2-1125

For x=1, y=1045

y=(1+5)^2-1125=36-1125=-1089\\\\But\ 1045\neq-1089

B)  y=(x-5)^2+1125

For x=1, y=1045

y=(1-5)^2+1125=14+1125=1139\\\But\ 1045\neq1139

C)   y=-5(x+5)^2-1125

y=-5(1+5)^2-1125=-5(36)-1125=-1305\\\\But\ 1045\neq-1305

D) y=-5(x-5)^2+1125

y=-5(1-5)^2+1125=-5(16)+1125=1045

Hence, this is the quadratic equation that models the data.

3 0
3 years ago
Read 2 more answers
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