The mean of 10 observations is 25. On checking, it was found that two of the observations were wrongly copied as 6 and 9. If the wrong observations are replaced by correct values 4 and 5, then the correct mean will be:

Correct option is B

Given:

Mean of 10 observations = 25

Wrong observations: 6 and 9

Correct observations: 4 and 5

Formula Used:

​$$\text{Correct Mean} = \frac{\text{Corrected Sum of Observations}}{\text{Number of Observations}}$$​

Solution:
Total sum based on wrong data = 25 × 10 = 250
Difference in values = (4 + 5) - (6 + 9) = 9 - 15 = -6
Corrected sum = 250 - 6 = 244

​$$\text{Correct Mean} = \frac{244}{10} = 24.4$$​