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forsale [732]
3 years ago
10

In a Scrabble tournament, the scores were normally distributed and the mean score was 420.2 points with a standard deviation of

105.0 points. What is the probability that the score of a randomly selected competitor differs from the mean score by less than 50 points
Mathematics
1 answer:
sveta [45]3 years ago
5 0

Answer:

P(370.2

And we can find this probability with this difference:

P(-0.762

Step-by-step explanation:

Let X the random variable that represent the scores of a population, and for this case we know the distribution for X is given by:

X \sim N(420.2,105)  

Where \mu=420.2 and \sigma=105

We are interested on this probability

P(X

And we can use the z score formula given by:

z=\frac{x-\mu}{\sigma}

And replacing we got:

P(370.2

And we can find this probability with this difference:

P(-0.762

You might be interested in
Solve 3k^2=8k+8,using completing the square method ​
GenaCL600 [577]

Answer:

3k2=8k+8 

Two solutions were found :

 k =(8-√160)/6=(4-2√ 10 )/3= -0.775

 k =(8+√160)/6=(4+2√ 10 )/3= 3.442

Reformatting the input :

Changes made to your input should not affect the solution:

 (1): "k2"   was replaced by   "k^2". 

Rearrange:

Rearrange the equation by subtracting what is to the right of the equal sign from both sides of the equation : 

                     3*k^2-(8*k+8)=0 

Step by step solution :

Step  1  :

Equation at the end of step  1  :

3k2 - (8k + 8) = 0

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  3k2-8k-8 

The first term is,  3k2  its coefficient is  3 .

The middle term is,  -8k  its coefficient is  -8 .

The last term, "the constant", is  -8 

Step-1 : Multiply the coefficient of the first term by the constant   3 • -8 = -24 

Step-2 : Find two factors of  -24  whose sum equals the coefficient of the middle term, which is   -8 .

     -24   +   1   =   -23     -12   +   2   =   -10     -8   +   3   =   -5     -6   +   4   =   -2     -4   +   6   =   2     -3   +   8   =   5     -2   +   12   =   10     -1   +   24   =   23

Observation : No two such factors can be found !! 

Conclusion : Trinomial can not be factored

Equation at the end of step  2  :

3k2 - 8k - 8 = 0

Step  3  :

Parabola, Finding the Vertex :

 3.1      Find the Vertex of   y = 3k2-8k-8

Parabolas have a highest or a lowest point called the Vertex .   Our parabola opens up and accordingly has a lowest point (AKA absolute minimum) .   We know this even before plotting  "y"  because the coefficient of the first term, 3 , is positive (greater than zero). 

 Each parabola has a vertical line of symmetry that passes through its vertex. Because of this symmetry, the line of symmetry would, for example, pass through the midpoint of the two  x -intercepts (roots or solutions) of the parabola. That is, if the parabola has indeed two real solutions. 

 Parabolas can model many real life situations, such as the height above ground, of an object thrown upward, after some period of time. The vertex of the parabola can provide us with information, such as the maximum height that object, thrown upwards, can reach. For this reason we want to be able to find the coordinates of the vertex. 

 For any parabola,Ak2+Bk+C,the  k -coordinate of the vertex is given by  -B/(2A) . In our case the  k  coordinate is   1.3333  

 Plugging into the parabola formula   1.3333  for  k  we can calculate the  y -coordinate : 

  y = 3.0 * 1.33 * 1.33 - 8.0 * 1.33 - 8.0 

or   y = -13.333

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = 3k2-8k-8

Axis of Symmetry (dashed)  {k}={ 1.33} 

Vertex at  {k,y} = { 1.33,-13.33}  

 k -Intercepts (Roots) :

Root 1 at  {k,y} = {-0.77, 0.00} 

Root 2 at  {k,y} = { 3.44, 0.00} 

Solve Quadratic Equation by Completing The Square

 3.2     Solving   3k2-8k-8 = 0 by Completing The Square .

 Divide both sides of the equation by  3  to have 1 as the coefficient of the first term :

   k2-(8/3)k-(8/3) = 0

Add  8/3  to both side of the equation : 

   k2-(8/3)k = 8/3

Now the clever bit: Take the coefficient of  k , which is  8/3 , divide by two, giving  4/3 , and finally square it giving  16/9 

Add  16/9  to both sides of the equation :

  On the right hand side we have :

   8/3  +  16/9   The common denominator of the two fractions is  9   Adding  (24/9)+(16/9)  gives  40/9 

  So adding to both sides we finally get :

   k2-(8/3)k+(16/9) = 40/9

Adding  16/9  has completed the left hand side into a perfect square :

   k2-(8/3)k+(16/9)  =

   (k-(4/3)) • (k-(4/3))  =

  (k-(4/3))2 

Things which are equal to the same thing are also equal to one another. Since

   k2-(8/3)k+(16/9) = 40/9 and

   k2-(8/3)k+(16/9) = (k-(4/3))2 

then, according to the law of transitivity,

   (k-(4/3))2 = 40/9

We'll refer to this Equation as  Eq. #3.2.1  

The Square Root Principle says that When two things are equal, their square roots are equal.

Note that the square root of

   (k-(4/3))2   is

   (k-(4/3))2/2 =

  (k-(4/3))1 =

   k-(4/3)

Now, applying the Square Root Principle to  Eq. #3.2.1  we get:

   k-(4/3) = √ 40/9 

Add  4/3  to both sides to obtain:

   k = 4/3 + √ 40/9 

Since a square root has two values, one positive and the other negative

   k2 - (8/3)k - (8/3) = 0

   has two solutions:

  k = 4/3 + √ 40/9 

   or

  k = 4/3 - √ 40/9 

Note that  √ 40/9 can be written as

  √ 40  / √ 9   which is √ 40  / 3 

Solve Quadratic Equation using the Quadratic Formula

 3.3     Solving    3k2-8k-8 = 0 by the Quadratic Formula .

 According to the Quadratic Formula,  k  , the solution for   Ak2+Bk+C  = 0  , where  A, B  and  C  are numbers, often called coefficients, is given by :

                                     

            - B  ±  √ B2-4AC

  k =   ————————

                      2A 

  In our case,  A   =     3

                      B   =    -8

                      C   =   -8 

Accordingly,  B2  -  4AC   =

                     64 - (-96) =

                     160

Applying the quadratic formula :

               8 ± √ 160 

   k  =    —————

                    6

Can  √ 160 be simplified ?

Yes!   The prime factorization of  160   is

   2•2•2•2•2•5  

To be able to remove something from under the radical, there have to be  2  instances of it (because we are taking a squarei.e. second root).

√ 160   =  √ 2•2•2•2•2•5   =2•2•√ 10   =

                ±  4 • √ 10 

  √ 10   , rounded to 4 decimal digits, is   3.1623

 So now we are looking at:

           k  =  ( 8 ± 4 •  3.162 ) / 6

Two real solutions:

 k =(8+√160)/6=(4+2√ 10 )/3= 3.442 

or:

 k =(8-√160)/6=(4-2√ 10 )/3= -0.775 

Two solutions were found :

 k =(8-√160)/6=(4-2√ 10 )/3= -0.775

 k =(8+√160)/6=(4+2√ 10 )/3= 3.442

5 0
3 years ago
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A craft project requires 3 pints of paint for every two students. About how many liters of paint are needed for 60 students? (2.
nadezda [96]

Answer:

90

Step-by-step explanation:

3/2=x/60

multiply 3/2 by 30 for the denominator to get to 60

90/60

90 liters of paint for 60 students

6 0
3 years ago
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The circumference of a circle is 407 cm. Find the diameter, the radius, the length of an arc of 100°, and the area of a sector w
iogann1982 [59]

Answer: 407cm =

100° =

100° =

I hope this helps :)

4 0
3 years ago
What is the perimeter?
Vladimir79 [104]

Answer:

Perimeter = 22 units

Area = 30 units squared

Step-by-step explanation: To find the perimeter of this figure, add the lengths of the rectangle's four sides (5+6+5+6=22). To find the area of this figure, multiply the length and width of the rectangle (5x6=30).

5 0
2 years ago
Find the next number in the number pattern 192,96,48,24
natima [27]
I got 12 because each time you are dividing the number in half. Half of 24 is 12.
3 0
3 years ago
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