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swat32
2 years ago
6

Two sections of a class took the same quiz. Section A had 15 students who had a mean score of 80, and Section B had 20 students

who had a mean score of 90. Overall, what was the approximate mean score for all of the students on the quiz?
A. 85.7
B. 85.0
C. none of these
D. 84.3
E. It cannot be determined
Mathematics
1 answer:
Nezavi [6.7K]2 years ago
7 0

Answer: A. 85.7

Step-by-step explanation:

Given : Two sections of a class took the same quiz.

Section A had 15 students who had a mean score of 80, and Section B had 20 students who had a mean score of 90.

We know that  , \text{Mean}=\dfrac{\text{Sum of observations}}{\text{No. of observations}}

Then , for section A :

\text{Mean score }=\dfrac{\text{Sum of scores in sec A}}{\text{No. of students}}

\Rightarrow\ 80=\dfrac{\text{Sum of scores in sec A}}{15}\\\\\Rightarrow\ \text{Sum of scores in sec A}=80\times15=1200

Similarly in Section B, \text{Sum of scores in sec B}=90\times20=1800

Total scores = Sum of scores in sec A+Sum of scores in sec B

=1200+1800=3000

Total students = Students in sec A +Students in sec B

=15+20=35

Now , the mean score for all of the students on the quiz =\dfrac{\text{Total score}}{\text{Total students}}

=\dfrac{3000}{35}=85.7142857143\approx85.7

Hence, the approximate mean score for all of the students on the quiz = 85.7

Thus , the correct answer is option A. 85.7.

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klasskru [66]

Answer:

\frac{4}{9}  

Step-by-step explanation:

\frac{2}{3} * \frac{2}{3}

you multiply across, so you do 2*2 for the numerator, then 3*3 for the denominator. This would equal 4 as the numerator, 9 as the denominator,  which is \frac{4}{9}  

4 0
2 years ago
HELP HELP ME PLS I AM RUNNING OUT OF TIME!!!! HERE IS MY PROBLEM:
kramer

Answer:

Step-by-step explanation:

To write fractions with a common denominator, you will most likely need to scale some numbers up! I will explain how.

Let's try it with the fractions

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12 is larger than 3, so we will have to multiply the 3 by some number to equal 12. (We are really finding the Least Common Multiple of the two denominators!) To do this, you have to multiply the 3 by 4, because 3x4=12. But now the numerator doesn't match the denominator. When you scale the denominator up, you have to scale the numerator up too! So the 2 must be multiplied by 4 also.

Now you have the following:

8

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These fractions now have common denominators! Now they're all set for adding or subtracting fractions.

Try another:

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: The least common multiple of 6 and 5 is 30. (the product of the denominators)

Transform each fraction by multiplying by "1":

2

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One last problem:

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7

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7 0
2 years ago
The mean life of a certain brand of auto batteries is 44 months with a standard deviation of 3 months. Assume that the lives of
alisha [4.7K]

Answer:

99.7%

Step-by-step explanation:

Using the z score formula

z-score is z = (x-μ)/σ

where:

x = raw score

μ = population mean

σ = population standard deviation.

a) for x = raw score = 35

μ = population mean = 44

σ = population standard deviation =3

z = (35 - 44)/3

z = -9/3

z = -3

b) for x = raw score = 53

μ = population mean = 44

σ = population standard deviation =3

z = (53 - 44)/3

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So P(-3<=Z<=3)=0.99865 - 0.0013499 = 0.9973

Converting to percentage = 0.9973 × 100 = 99.73%

Therefore, the percentage of auto batteries of this brand that have a life of 35 to 53 months to one decimal place is 99.7%

6 0
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I am not understanding the question would you like a fraction????
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