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almond37 [142]
3 years ago
9

A standard fluorescent tube has a life length that is normally distributed with a mean of 7000 hours and a standard deviation of

1000 hours. A competitor has developed a compact fluorescent lighting system that will fit into incandescent sockets. It claims that a new compact tube has a normally distributed life length with a mean of 7500 hours and a standard deviation of 1200 hours.
1. Which fluorescent tube is more likely to have a life length greater than 9000 hours?
Mathematics
1 answer:
adell [148]3 years ago
7 0

Answer:

The new compact tube is more likely to have a life length greater than 9000 hours.

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the zscore of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

Standard tube:

\mu = 7000, \sigma = 2000

New compact tube:

\mu = 7500, \sigma = 1200

1. Which fluorescent tube is more likely to have a life length greater than 9000 hours?

Whichever tube has the lower z-score when X = 9000, since the probability of having a life length greater than 9000 hours is 1 subtracted by the pvalue of Z when X = 9000. The higer z, the higher it's pvalue.

Standard tube:

Z = \frac{X - \mu}{\sigma}

Z = \frac{9000 - 7000}{1000}

Z = 2

New compact tube:

Z = \frac{X - \mu}{\sigma}

Z = \frac{9000 - 7500}{1200}

Z = 1.25

The new compact tube is more likely to have a life length greater than 9000 hours.

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A jumping spider's movement is modeled by a parabola. The spider makes a single jump from the origin and reaches a maximum heigh
Stella [2.4K]

A parabola is a mirror-symmetrical U-shape.

  • The equation of the parabola is \mathbf{y = -\frac{1}{640}(x - 80)^2 + 10}
  • The focus is \mathbf{Focus = (80, -1760)}
  • The directrix is \mathbf{y = \frac{1}{640}}
  • The axis of the symmetry of parabola is: \mathbf{x = 80}

From the question, we have:

\mathbf{Vertex: (h,k) = (80,10)}

\mathbf{Origin: (x,y) = (0,0)}

The equation of a parabola is:

\mathbf{y = a(x - h)^2 + k}

Substitute the values of origin and vertex in \mathbf{y = a(x - h)^2 + k}

\mathbf{0 = a(0 - 80)^2 + 10}

\mathbf{0 = a(- 80)^2 + 10}

\mathbf{0 = 6400a + 10}

Collect like terms

\mathbf{6400a =- 10}

Solve for a

\mathbf{a =- \frac{1}{640}}

Substitute the values of a and the vertex in \mathbf{y = a(x - h)^2 + k}

\mathbf{y = -\frac{1}{640}(x - 80)^2 + 10}

The focus of a parabola is:

\mathbf{Focus = (h, \frac{k+1}{4a})}

Substitute the values of a and the vertex in \mathbf{Focus = (h, \frac{k+1}{4a})}

\mathbf{Focus = (80, \frac{10+1}{4 \times -\frac{1}{640}})}

\mathbf{Focus = (80, -\frac{11}{\frac{1}{160}})}

\mathbf{Focus = (80, -11\times 160)}

\mathbf{Focus = (80, -1760)}

The equation of the directrix is:

\mathbf{y = -a}

So, we have:

\mathbf{y = \frac{1}{640}} ----- the directrix

The axis of symmetry is:

\mathbf{x = -\frac{b}{2a}}

We have:

\mathbf{y = -\frac{1}{640}(x - 80)^2 + 10}

Expand

\mathbf{y = -\frac{1}{640}(x^2 -160x + 6400) +10}

Expand

\mathbf{y = -\frac{1}{640}x^2 +\frac{1}{4}x - 10 +10}

\mathbf{y = -\frac{1}{640}x^2 +\frac{1}{4}x }

A quadratic function is represented as:

\mathbf{y = ax^2 + bx + c}

So, we have:

\mathbf{a = -\frac{1}{640}}

\mathbf{b = \frac{1}{4}}

Recall that:

\mathbf{x = -\frac{b}{2a}}

So, we have:

\mathbf{x = -\frac{1/4}{2 \times -1/640}}

\mathbf{x = \frac{1/4}{1/320}}

This gives

\mathbf{x = \frac{320}{4}}

\mathbf{x = 80}

Hence, the axis of the symmetry of parabola is: \mathbf{x = 80}

Read more about parabola at:

brainly.com/question/21685473

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The following table represents a function.
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The answer is B. Plug in the x values to check the y values.
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Can I get help on this please
Misha Larkins [42]

Answer:

5. You can round question a up to 100 + 55 (then do the counting)

5. You can round question b up to 245 - 100 (then do the counting)

You can round question c up to 100 x 5 (then do the counting)

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Please rank Brainliest if this helps!

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- 30 = 12 – 6r<br><br> Pls help
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Answer: r = 7

Step-by-step explanation:

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2. A chemist has a 25% and a 50% acid solution. How
AnnZ [28]

Answer:

x is mL of 25% acid and y is mL of 50% acid

We set up 2 equations:

A) x + y = 250

B) .25 x + .50y = .35 * 250 which equals

B) .25x + .50y = 87.50  Multiplying A) by -.5

A) -.5x -.5y = -125  adding the equations we get

-.25x = -37.50

x = 150 mL

y = 100 mL

Source:  http://www.1728.org/mixture.htm

Step-by-step explanation:

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