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A study of long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the l

lesya692 [45]

Answer:

The probability that a call last between 4.2 and 4.9 minutes is 0.4599

Step-by-step explanation:

Let X be the length in minutes of a random phone call. X is a normal distribution with mean λ=4.2 and standard deviation σ=0.4. We want to know P(4.2 < X < 4.9). In order to make computations, we will use W, the standarization of X, given by the following formula

$W = \frac{X-\mu}{\sigma} = \frac{X-4.2}{0.4}$

We will use $\phi$ , the cummulative distribution function of W. The values of $\phi$ are well known and the can be found in the attached file

$P(4.2 < X < 4.9) = P(\frac{4.2-4.2}{0.4} < \frac{X-4.2}{0.4} < \frac{4.9-4.2}{0.4}) = P(0 < W < 1.75) = \\ \phi(1.75) - \phi(0) = 0.9599-0.5 = 0.4599$

We conclude that the probability that a call last between 4.2 and 4.9 minutes is 0.4599

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7 0

3 years ago

Chris is calculating his deductions for his tax return. He is filing singly. He can claim $1,813 from property taxes, $1,513 fro

zalisa [80]

The standard deduction compare to Chris’s deductions is letter D which is "<span>The standard deduction is $664 better than Chris’s deductions."

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5 0

3 years ago

Simplify 4√1/32 - 2√1/8

Molodets [167]

Answer would be -0.125 I think I hope so:)

8 0

3 years ago

Read 2 more answers

when 6 is subtracted from the square of a number, the result is 5 times the number. Find the negative solution.

sveta [45]

When 6 is subtracted from the square of a number, the result is 5 times the number, then the negative solution is -1

<h3><u>Solution:</u></h3>

Given that when 6 is subtracted from the square of a number, the result is 5 times the number

To find: negative solution

Let "a" be the unknown number

Let us analyse the given sentence

square of a number = $a^2$

6 is subtracted from the square of a number = $a^2 - 6$

5 times the number = $5 \times a$

<em><u>So we can frame a equation as:</u></em>

6 is subtracted from the square of a number = 5 times the number

$a^2 - 6 = 5 \times a\\\\a^2 -6 -5a = 0\\\\a^2 -5a -6 = 0$

<em><u>Let us solve the above quadratic equation</u></em>

For a quadratic equation $ax^2 + bx + c = 0$ where $a \neq 0$

$x=\frac{-b \pm \sqrt{b^{2}-4 a c}}{2 a}$

Here in this problem,

$a^2-5 a-6=0 \text { we have } a=1 \text { and } b=-5 \text { and } c=-6$

Substituting the values in above quadratic formula, we get

$\begin{array}{l}{a=\frac{-(-5) \pm \sqrt{(-5)^{2}-4(1)(-6)}}{2 \times 1}} \\\\ {a=\frac{5 \pm \sqrt{25+16}}{2}=\frac{5 \pm \sqrt{49}}{2}} \\\\ {a=\frac{5 \pm 7}{2}}\end{array}$