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

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Joined: 11 Feb 2015
Posts: 712

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27 Sep 2018, 08:04
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Difficulty:

45% (medium)

Question Stats:

68% (01:37) correct 32% (01:43) wrong based on 59 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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27 Sep 2018, 13:13

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
Re: If the average (arithmetic mean) grade of x students...   [#permalink] 27 Sep 2018, 13:13
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