A pupil's marks were wrongly entered as 83 instead of 70. Due to the average marks for the class got increased by half. The number of pupils in the class is?
Choose one:  A) 18  B) 82  C) 26  D) 27  E) 29

Rationale: "let there be x pupils in the class . total increase in marks = ( x * 1 / 2 ) = x / 2 x / 2 = ( 83 - 70 ) = > x / 2 = 13 = > x = 26 . answer : c"
Answer: C