Find the total average marks of all the students in 2 separate classes, if the average marks of students in the first class of 39 students is 45 and that of another class of 35 students is 70.	Choose the correct choice from the following options.
A) 55.8
B) 51.8
C) 53.8
D) 56.8
E) 52.8

Rationale: sum of the marks for the class of 39 students = 39 * 45 = 1755 sum of the marks for the class of 35 students = 35 * 70 = 2450 sum of the marks for the class of 74 students = 1755 + 2450 = 4205 average marks of all the students = 4205 / 74 = 56.8 answer : d
Answer: D