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Artyom0805 [142]
3 years ago
12

Find the percent of decrease 20 to 15

Mathematics
1 answer:
marshall27 [118]3 years ago
3 0

Answer:

25%

Step-by-step explanation:

I look it up and made sure trust its right

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5 0
3 years ago
Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.2.a. If the distri
zalisa [80]

Answer:

a

 P(\= X \ge 51 ) =0.0062

b

P(\= X \ge 51 ) = 0

Step-by-step explanation:

From the question we are told that

The mean value is \mu = 50

The standard deviation is  \sigma = 1.2

Considering question a

The sample size is  n = 9

Generally the standard error of the mean is mathematically represented as

      \sigma_x = \frac{\sigma }{\sqrt{n} }

=>   \sigma_x = \frac{ 1.2 }{\sqrt{9} }

=>  \sigma_x = 0.4

Generally the probability that the sample mean hardness for a random sample of 9 pins is at least 51 is mathematically represented as

      P(\= X \ge 51 ) = P( \frac{\= X - \mu }{\sigma_{x}}  \ge \frac{51 - 50 }{0.4 } )

\frac{\= X -\mu}{\sigma }  =  Z (The  \ standardized \  value\  of  \ \= X )

     P(\= X \ge 51 ) = P( Z  \ge 2.5 )

=>   P(\= X \ge 51 ) =1-  P( Z  < 2.5 )

From the z table  the area under the normal curve to the left corresponding to  2.5  is

    P( Z  < 2.5 ) = 0.99379

=> P(\= X \ge 51 ) =1-0.99379

=> P(\= X \ge 51 ) =0.0062

Considering question b

The sample size is  n = 40

   Generally the standard error of the mean is mathematically represented as

      \sigma_x = \frac{\sigma }{\sqrt{n} }

=>   \sigma_x = \frac{ 1.2 }{\sqrt{40} }

=>  \sigma_x = 0.1897

Generally the (approximate) probability that the sample mean hardness for a random sample of 40 pins is at least 51 is mathematically represented as  

       P(\= X \ge 51 ) = P( \frac{\= X - \mu }{\sigma_x}  \ge \frac{51 - 50 }{0.1897 } )

=> P(\= X \ge 51 ) = P(Z  \ge 5.2715  )

=>  P(\= X \ge 51 ) = 1- P(Z < 5.2715  )

From the z table  the area under the normal curve to the left corresponding to  5.2715 and

=>  P(Z < 5.2715  ) = 1

So

   P(\= X \ge 51 ) = 1- 1

=> P(\= X \ge 51 ) = 0

5 0
3 years ago
I need some help with this question
vitfil [10]
(0,7) would be located on the y axis
4 0
3 years ago
ANSWER ASAP The area of a rectangle depends on its length and width. For the area to remain constant, the length varies inversel
Free_Kalibri [48]
Area of the rectangle is equal to length times width

In function notation, the Area of the rectangle function is a function in variables l (length) and w(width) as follows:

A(l, w)= l*w

for A=475 we have,

l*w=475

l= \frac{475}{w} or w= \frac{475}{l} , each are equivalent, and each represent the inverse variation.


Answer: l= \frac{475}{w} , w= \frac{475}{l} 


4 0
3 years ago
Please help. 50 Points.
Ronch [10]

Answer:

0.8745.

Step-by-step explanation:

P(success) = 0.09 and P(failure) = 1 - 0.09 = 0.91.

P( at least 6 failures) = P( less than 2 successes)

= 7C0 (0.09)^0 (0.91)^7 + 7C1 (0.09)(0.91)^6

=  0.5168 + 0.3577

= 0.8745.

8 0
4 years ago
Read 2 more answers
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