The average marks of 100 students are given to be 40

Averages

The average marks of 100 students are given to be 40. It was found later that marks of one student were 53 which were misread as 83. The corrected mean marks are

  1. 39
  2. 39.7
  3. 40
  4. 40.3

Answer

Total marks = Average × Number of students

Total marks = 40 × 100 = 4000

Corrected total marks = 4000 - 83 + 53 = 3970

New average = 3970/100 = 39.7

Alternate Solution

Difference of total marks = 83 - 53 = 30

Difference in average = 30/100 = 0.3

New average = 40 - 0.3 = 39.7

The correct option is B.