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If the average (arithmetic mean) grade of x students...

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If the average (arithmetic mean) grade of x students...  [#permalink]

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New post 27 Sep 2018, 09:04
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Question Stats:

57% (01:43) correct 43% (01:45) wrong based on 47 sessions

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If the average (arithmetic mean) grade of \(x\) students in a particular class is 90, what is the average (arithmetic mean) grade received by the left-handed students?

1) There are a total of 20 students in the class.

2) There are \(\frac{x}{5}\) right-handed students in the class; together, they receive an average score of 95.

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Re: If the average (arithmetic mean) grade of x students...  [#permalink]

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New post 27 Sep 2018, 14:13
Question asks us to find the mean grade received by the left-handed students?

If the mean grade of x students in a particular class is 90
Formula for Mean = Total sum/n or Total sum = mean *n
Given
Number of students (n)=x
Total sum = 90x

1) There are a total of 20 students in the class.
You cant find the left-handed students average with this.... all we can say is 20*90 is the total sum of grades in the class.
Not sufficient

2) There are x/5 right-handed students in the class; together, they receive an average score of 95.
So left handed student should be 4/5.

Sum of grades of right handed students =mean * number of students= 95*x/5 = 14x

Total sum of grades of students in class - total sum of grades of right handed students = total grades of left handed students

90x-14x = 76x = total grades of left handed students

Mean = Total grades of left handed students / total number of students
= 76x/(4x/5) = (76x*5)/4x = 85

Thus Sufficient B
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Re: If the average (arithmetic mean) grade of x students... &nbs [#permalink] 27 Sep 2018, 14:13
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If the average (arithmetic mean) grade of x students...

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