A student's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half. The number of students in the class is:
Answer: C
The extra marks added to the total sum = 83 - 63 = 20.
Let N be the number of students. The increase in the total sum (20) caused the average to increase by 1/2.
Increase in average = \(\frac{\text{Increase in sum}}{\text{Number of students}}\)
\(\frac{1}{2} = \frac{20}{N}\)
N = 20 × 2 = 40.
There are 40 students in the class.