If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 60, then the average marks of all the students is__________?

A. 53.33
B. 54.68
C. 55
D. None of these

Required average = (55 x 50 + 60 x 55 + 45 x 60) / (55 + 60 + 45)
= (2750 + 3300 + 2700) /160
= 54.68 is correct Answer