The average mark in a class of 25 students in the geography exam is 64. If the marks of three students were misread as 44, 46, and 61 instead of the actual marks 54, 64, and 67 respectively, then find the correct average.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4. i.e. 65.36.
We know that,
Average = Sum of observations/Number of observations
Sum of marks in geography = 64 × 25 = 1600
Change in sum because of misread of marks = 1600 - 44 - 46 - 61 + 54 + 64 + 67 = 1634
The correct average = 1634/25 = 65.36