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:	Choose the correct choice from the following answers:
A) 32
B) 50
C) 40
D) 20
E) 10

Rationale: "let there be x pupils in the class . total increase in marks = x x 1 / 2 = x / 2 x / 2 = ( 83 - 63 ) x / 2 = 20 x = 40 . answer : c"
Answer: C