The mean of the marks scored by 50 students was found to be 39. Later on it was discovered that a score

of 43 was misread as 23. Find the correct mean.

Question

The mean of the marks scored by 50 students was found to be 39 Later on it was discovered that a score of 43 was misread as 23 Find the correct mean

Accepted Answer

It is given that

Mean of the marks of 50 students = 39

So we get

Sum of these marks = 39 (50) = 1950

We can write it as

Corrected sum of the marks = 1950 – wrong number + correct number

By substituting the values

Corrected sum of the marks = 1950 – 23 + 43

So we get

Corrected sum of the marks = 1970

So the correct mean = 1970/50

By division

Correct mean = 39.4

Therefore, the correct mean is 39.4.

RS Aggarwal Solutions Class 9 Mathematics Solutions for Mean Median And Mode Of Ungrouped Data Exercise 18A in Chapter 18 - Mean Median And Mode Of Ungrouped Data