The mean marks obtained by 300 students in a subject are 60

The mean marks obtained by 300 students in a subject are 60. The mean of top 100 students was found to be 80 and the mean of last 100 students was found to be 50. The mean marks of the remaining 100 students are

  1. 70
  2. 65
  3. 60
  4. 50

Answer

Let mean marks of remaining 100 students be M.

Mean = ∑(fx) / ∑f = 60

∑f = 300

∑(fx) = 100×80 + 100×M + 100×50 = 100(130 + M)

60 = 100(130 + M)/300

180 = 130 + M

M = 50

The correct option is D.