While the marks scored by the students of a class in an examination were being noted down, the marks of one student were recorded by mistake as 96 instead of 69. Because of this, the average marks increased by 0.3. How many students are there in the class?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 90
An error in one entry changes the total by the size of the error, and the average changes by that amount divided by the number of students.
Extra marks added to the total by the mistake \(=96-69=27\)
Rise in the average \(=0.3\)
\(\displaystyle \text{Number of students}=\frac{27}{0.3}=90\)
There are 90 students in the class.