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:

Problem Restatement

One mark was overstated by 20 points (83 instead of 63). This increased the average by 0.5. Find the class size.

Concept / Approach

Average increase = (Total error) ÷ (Number of students).

Step-by-step calculation

Total error = 83 − 63 = 20Let number of students be nIncrease in average = 0.5 = 20 ÷ n → n = 20 ÷ 0.5 = 40

Final Answer

Number of students in the class = 40.