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murzikaleks [220]
3 years ago
14

The time needed to complete a final examination in a particular college course is normally distributed with a mean of 77 minutes

and a standard deviation of 12 minutes. Answer the following questions.
Required:
a. What is the probability of completing the exam in one hour or less (to 4 decimals).
b. What is the probability that a student will complete the exam in more than 60 minutes but less than 75 minutes (to 4 decimals)?
c. Assume that the class has 60 students and that the examination period is 90 minutes in length. How many students do you expect will be unable to complete the exam in the allotted time (to the nearest whole number)?
Mathematics
1 answer:
Komok [63]3 years ago
6 0

Answer:

a. The probability of completing the exam in one hour or less is 0.0783

b. The probability that student will complete the exam in more than 60 minutes but less than 75 minutes is 0.3555

c. The number of students will be unable to complete the exam in the allotted time is 8

Step-by-step explanation:

a. According to the given we have the following:

The time for completing the final exam in a particular college is distributed normally with mean (μ) is 77 minutes and standard deviation (σ) is 12 minutes

Hence, For X = 60, the Z- scores is obtained as follows:

Z=  X−μ /σ

Z=60−77 /12

Z=−1.4167

Using the standard normal table, the probability P(Z≤−1.4167) is approximately 0.0783.

P(Z≤−1.4167)=0.0783

Therefore, The probability of completing the exam in one hour or less is 0.0783.

b. In this case For X = 75, the Z- scores is obtained as follows:

Z=  X−μ /σ

Z=75−77 /12

Z=−0.1667

Using the standard normal table, the probability P(Z≤−0.1667) is approximately 0.4338.

Therefore, The probability that student will complete the exam in more than 60 minutes but less than 75 minutes is obtained as follows:

P(60<X<75)=P(Z≤−0.1667)−P(Z≤−1.4167)

=0.4338−0.0783

=0.3555

​

Therefore, The probability that student will complete the exam in more than 60 minutes but less than 75 minutes is 0.3555

c. In order to compute  how many students you expect will be unable to complete the exam in the allotted time we have to first compute the Z−score of the critical value (X=90) as follows:

Z=  X−μ /σ

Z=90−77 /12

Z​=1.0833

UsING the standard normal table, the probability P(Z≤1.0833) is approximately 0.8599.

Therefore P(Z>1.0833)=1−P(Z≤1.0833)

=1−0.8599

=0.1401

​

Therefore, The number of students will be unable to complete the exam in the allotted time is= 60×0.1401=8.406

The number of students will be unable to complete the exam in the allotted time is 8

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Convert this number given in standard form into scientific notation. 0. 0000069 What is the value in scientific notation? 0. 69
Len [333]

Scientific notation is used so that the order of the number is known in first glance. The value of the given number in scientific notation is given by: Option B: 6.9 \times 10^{-6}

<h3>How does scientific notations work?</h3>

The number is written in the form a \times 10^b where we have 1 \leq a < 10

The number b shows the order, which is the most important figure for which scientific notation is used. It tells us how much order large or small a value is in powers of 10. We can for a time, ignore the value of 'a' for two comparable quantities and only compare their orders(this type of comparison is useful when difference is too big, like size of human to size of a star etc sort of comparisons).

Scientific notations have some of the profits as:

  • Better readability due to compact representation
  • Its value in terms of power of 10 is known, which helps in easy comparison of quantities differing by a large value.


For the given case, the number in consideration is 0.0000069

Rewriting it in fraction form, we get:

0.0000069  = \dfrac{69}{10000000} = \dfrac{69}{10^7} = 69 \times 10^{-7} = 6.9 \times 10 \times 10^{-7}\\\\0.0000069  =  6.9 \time 10 ^{-7 +1} \\0.0000069  = 6.9\times 10^{-6}

(we used two facts: first that : \dfrac{a}{b} = a \times \dfrac{1}{b}

and second that: a^{-b}= \dfrac{1}{a^b}

Thus, the value of the given number in scientific notation is given by: Option B: 6.9 \times 10^{-6}

Learn more about scientific notations here:

brainly.com/question/3112062

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