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Alona [7]
3 years ago
8

A large manufacturing plant uses lightbulbs with lifetimes that are normally distributed with a mean of 1200 hours and a standar

d deviation of 60 hours. To minimize the number of bulbs that burn out during operating hours, all bulbs are replaced at once. How often should the bulbs be replaced so that no more than 1% burn out between replacement periods? (Round your answer to one decimal place.)
Mathematics
1 answer:
a_sh-v [17]3 years ago
4 0

Answer:

The bulbs should be replaced each 1060.5 days.

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:

\mu = 1200, \sigma = 60

How often should the bulbs be replaced so that no more than 1% burn out between replacement periods?

This is the first percentile, that is, the value of X when Z has a pvalue of 0.01. So X when Z = -2.325.

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

-2.325 = \frac{X - 1200}{60}

X - 1200 = -2.325*60

X = 1060.5

The bulbs should be replaced each 1060.5 days.

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Answer:

The value is  v =  49.23 \  mph

Step-by-step explanation:

From the question we are told that

  The  distance from Jacksonville to Miami is  d  =  382 miles

  The  time it take to travel from Jacksonville to Daytona is  t_1  = 1 \ hour\ and\ 54\ minutes = 1 + \frac{54}{60} =  1.9 \  hours

  The  time it take to travel from Daytona Beach to Fort Pierce is t_2  = 2\ hours\ and\ 51\ minutes= 2 + \frac{51}{60} =  2.85 \  hours

    The  time it take to travel from Fort Pierce to West Palm Beach is  

t_3  = 1\ hour\ and\ 23\ minutes= 1 + \frac{23}{60} =  1.38 \  hours

     The  time it take to travel from West Palm Beach to Miami t_4  = 1\ hour\ and\ 38\ minutes= 1 + \frac{38}{60} =  1.63 \  hours

Generally the average speed is mathematically represented as

      v  =  \frac{d}{t_1 + t_2 +t_3 + t_4 }

=>   v  =  \frac{382}{1.9  + 2.85 +1.38 + 1.63 }

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<h3>Answer:</h3>

The circle makes the larger area

The difference in the two areas is roughly 132.2479 square feet.

=================================================

Explanation:

If Carter decides to go for a circle, then 88 is the circumference, which is the distance around the circle (aka perimeter of the circle).

Use this to find the radius needed

C = 2*pi*r

r = C/(2pi)

r = 88/(2pi)

r = 44/pi

I'll leave it in exact form rather than approximate it.

Once we know the radius, we can find the area of the circle.

A = pi*r^2

A = pi(44/pi)^2

A = pi*(1936/(pi^2))

A = 1936/pi

A = 616.247939651819 approximately

I used my calculator's stored version of pi to compute the area in the final step.

We'll be comparing this number later, so hold onto it for now.

-------------------------------------

If Carter instead decides for a square, then 88 is the perimeter since it's the amount of fencing he has to work with.

Divide it into 4 pieces to find the length of each side of the square (all sides are equal in a square)

88/4 = 22

Each side is 22 feet

The area of this square is (22)^2 = 22*22 = 484 square feet

--------------------------------------

Summary:

  • If Carter goes for a circular enclosure, then he gets roughly 616.2479 square feet.
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The circle wins in terms of larger area.

The difference being roughly 616.2479  - 484 = 132.2479 square feet.

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