The average marks of a class of 30 students is 40 and that of another class of 50 students is 60. Find the average marks of all the students?
Select the correct option:
A) 82.5	B) 52.9	C) 52.2	D) 52.5	E) 52.7

Rationale: "sum of the marks for the class of 30 students = 30 * 40 = 1200 sum of the marks for the class of 50 students = 50 * 60 = 3000 sum of the marks for the class of 80 students = 1200 + 3000 = 4200 average marks of all the students = 4200 / 80 = 52.5 answer : d"
Answer: D