If the average marks of three batches of 55, 60 and 45 students respectively is 45, 55, 60, then the average marks of all the students is:  Select.
A) 53.33  B) 54.68  C) 52.97  D) 56  E) None of these
Explanation:   Required average = (55 × 45 + 60 × 55 + 45 × 60/55 + 60 + 45)   = (2475 + 3300 + 2700/160)   = 8475/160   = 52.97   Answer: 52.97
<result>C</result>
If the average marks of three batches of 55, 60 and 45 students respectively is 45, 55, 60, then the average marks of all the students is: