The average marks of a class of 35 students is 40 and that of another class of 45 students is 60. Find the average marks of all the students? Choices:
A) 52.6
B) 52.4
C) 52.1
D) 51.2
E) 52.9

Rationale: "sum of the marks for the class of 35 students = 35 * 40 = 1400 sum of the marks for the class of 45 students = 45 * 60 = 2700 sum of the marks for the class of 80 students = 1400 + 2700 = 4100 average marks of all the students = 4100 / 80 = 51.2 . answer : d"
Answer: D