If the average marks of 3classes of 55, 60 and 45 students respectively is 50, 55, 60, then find the average marksof all the students is  Choose the correct choice from the following choices
A) 53	B) 53.5	C) 54.68	D) 55.6	E) 67.2

Rationale: required average = 55 x 50 + 60 x 55 + 45 x 60 55 + 60 + 45 = 2750 + 3300 + 2700 160 = 8750 160 = 54.68 c
Answer: C