Question

The average marks of 40 students in an examination was 34. it was later found that the marks of one student had been wrongly entered as 62 instead of 26. what is the correct average?

Answer 1

Given;
The average marks of 40 students in an examination =34
It was found that one student had been wrongly entered as 62 instead of 26.
The marks of students in an examination=40*34=1360
62-26=36
1360-36=1324
After correction of marks the mean =1324/40
=33.1
After correction of marks the mean is 33.1

Answer 2

Answer:

Here ,The average marks secured by 36 students = 52

Difference of correct and incorrect marks = 64 – 46 = 18

∴ Correct mean = 52 +

18

36

Correct mean = 52.5

Second method to solve this question with the help of given formula :

Here, n = 36, m = 52 , a = 64, b = 46

New mean = m +

(a - b)

n

New mean = 52 +

(64 - 46)

36

New mean = 52 +

18

36

New mean = 52 +

1

= 52.5

2