The average marks of a class of 25 students is 40 and that of another class of 30 students is 60. Find the average marks of all the students?
Choices:
A) 52.6
B) 52.4
C) 52.1
D) 50.9
E) 52.9

Rationale: "sum of the marks for the class of 25 students = 25 * 40 = 1000 sum of the marks for the class of 30 students = 30 * 60 = 1800 sum of the marks for the class of 55 students = 1000 + 1800 = 2800 average marks of all the students = 2800 / 55 = 50.9 . answer : d"
Answer: D