The average marks of a class of 12 students is 40 and that of another class of 28 students is 60. Find the average marks of all the students?  Answers:
A) 52.2 B) 59.5 C) 52.8 D) 52.5 E) 54.0

Rationale: "sum of the marks for the class of 12 students = 12 * 40 = 480 sum of the marks for the class of 28 students = 28 * 60 = 1680 sum of the marks for the class of 40 students = 480 + 1680 = 2160 average marks of all the students = 2160 / 40 = 54 answer : e"
Answer: E