While the marks scored by the students of a class in an examination were being recorded, the marks of one student were entered by mistake as 86 instead of 68. Because of this, the average marks increased by 0.6. How many students are there in the class?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 30
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 \(=86-68=18\)
Rise in the average \(=0.6\)
Number of students \(\displaystyle =\frac{18}{0.6}=30\)
There are 30 students in the class.