Question

The marks obtained by a student were entered as 78 instead of 68. Due to this, the average marks of the class increased by 0.5 marks. How many students are there in the class?

1. 20
2. 30
3. 35
4. 25

Answer 1

Correct Answer - Option 1 : 20

Given:

The increase in average = 0.5

The marks obtained by a student were entered as 78 instead of 68

Concept used:

Average = (Sum of observations)/(Number of observations)

Calculation:

Let the total number of students be x.

The increase in average = 0.5

Increase in total mark = x × 0.5 = 0.5x

Increase in total marks = 78 – 68 = 10

∴ 0.5x = 10

⇒ x = 10/0.5

⇒ x = 20

∴ The total number of students in the class is 20.