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2 years ago

7

Scores on a test have a mean of 66 and Q3 is 80. The scores have a distribution that is approximately normal. Find the standard

deviation. Round your answer to the nearest tenth.
A) 10.5
B) 20.9
C) 9.4
D) 18.7

1 answer:

Troyanec [42]2 years ago

6 0

The correct answer is B

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3 years ago

Let a and b be roots of x² - 4x + 2 = 0. find the value of a/b² +b/a²

erastovalidia [21]

Answer:

$\dfrac{a}{b^2}+\dfrac{b}{a^2}=10$

Step-by-step explanation:

Given equation: $x^2-4x+2=0$

The roots of the given quadratic equation are the values of x when $y=0$ .

To find the roots, use the quadratic formula:

$x=\dfrac{-b \pm \sqrt{b^2-4ac} }{2a}\quad\textsf{when }\:ax^2+bx+c=0$

Therefore:

$a=1, \quad b=-4, \quad c=2$

$\begin{aligned}\implies x & =\dfrac{-(-4) \pm \sqrt{(-4)^2-4(1)(2)}}{2(1)}\\& =\dfrac{4 \pm \sqrt{8}}{2}\\& =\dfrac{4 \pm 2\sqrt{2}}{2}\\& =2 \pm \sqrt{2}\end{aligned}$

$\textsf{Let }a=2+\sqrt{2}$

$\textsf{Let }b=2-\sqrt{2}$

Therefore:

$\begin{aligned}\implies \dfrac{a}{b^2}+\dfrac{b}{a^2} & = \dfrac{2+\sqrt{2}}{(2-\sqrt{2})^2}+\dfrac{2-\sqrt{2}}{(2+\sqrt{2})^2}\\\\& = \dfrac{2+\sqrt{2}}{6-4\sqrt{2}}+\dfrac{2-\sqrt{2}}{6+4\sqrt{2}}\\\\& = \dfrac{(2+\sqrt{2})(6+4\sqrt{2})+(2-\sqrt{2})(6-4\sqrt{2})}{(6-4\sqrt{2})(6+4\sqrt{2})}\\\\& = \dfrac{12+8\sqrt{2}+6\sqrt{2}+8+12-8\sqrt{2}-6\sqrt{2}+8}{36+24\sqrt{2}-24\sqrt{2}-32}\\\\& = \dfrac{40}{4}\\\\& = 10\end{aligned}$

6 0

1 year ago

Read 2 more answers

NemiM [27]

it is 2y 1x, good luck, hope i helped!!!

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3 years ago

A fair owner made $60 win a group of 10 people entered which is a rate of ____ dollar per person?

melisa1 [442]

Answer:

It would be 6$ each person

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3 years ago

How do I find the volume?

kotykmax [81]

Answer:

14ft

First get the cones volume formula v=(3.14*r^2*h)/3

Second find the radius which is 1/2 the diameter.

Third plug in given and solve 366= (3.14*5^2*h)/3

366*3=3*(3.14*25*h)/3

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1098/78.5=78.5h/78.5

13.987=h

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3 years ago