# 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

Question 7 Mean Median And Mode Of Ungrouped Data Exercise 18A

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.

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.

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