A pupil's marks were wrongly entered as 83 instead of 63. Due to that the…
20252025
A pupil's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half (1/2). The number of pupils in the class is __
- A.
10
- B.
20
- C.
40
- D.
73
Attempted by 15 students.
Show answer & explanation
Correct answer: C
Let n be the number of pupils in the class.
The mistaken entry changes a pupil's mark from 63 to 83, increasing the total marks by 83 − 63 = 20.
This increases the class average by (increase in total)/n = 20/n, and we are told the average increased by 1/2.
Set up the equation: 20/n = 1/2.
Solve for n: n = 20 ÷ (1/2) = 20 × 2 = 40.
Therefore the number of pupils in the class is 40.