Question

The mean of marks scored by 100 students was found to be 40. Later on it was discovered
that a score of 53 was misread as 83. Find the correct mean.

Answer 1

Mean marks of 100 students = 40
  ⇒Sum of marks of 100 students 100×40×4000

Correct value 53.
Incorrect value 83. 
Correct sum = 4000-83+53
                   = 3970

∴ Correct mean =`3970/100`

                        = 39.7