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Ayisha posted an Question
April 07, 2020 • 16:07 pm 20 points
  • UGC NET
  • Commerce

2. a group of 210 students appeared in some test. the mean of 1/3 rd of students is found to be 60. the mean of the remaining students is found to be 78. the me

2. A group of 210 students appeared in some test. The mean of 1/3 rd of students is found to be 60. The mean of the remaining students is found to be 78. The mean of the whole group will be: (1) 80 (2) 76 (3) 74 (4) 72

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    Rishab Soni Best Answer

    The mean of 1/3 of the student is 60 = The mean of 1/3 of the students of 210 is 60 = The mean of 70 students is 60 = Total score of 60 students = 60 X 70 = 4200 (1) Total mean of rest (2/3) of the students = Total score of 140 students is 78 X 140 = 10920 Total Score of the group is (10920 + 4200) / 210 = 72. The mean of the whole group is 72.

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    To calculate the mean, we have formula Total Score / Toal number. We already have total number as 210. Now we need total score. For tha, the next info provided is 1/3 of students have mean of 60. Meaning total score of 70 students/70 is 60. To calculate total score of 70 students, we multiply 70 with 60 (number with mean) and we get 4200 (1), Repeating the same with the next data for remaining 140 students, we get the total score as 10920 (2) . Now we can calculate the total score by adding (1) and (2) which should give us 15120. Divide that with total number of students (210) and we'll get mean as 72.

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