If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 65, then the average marks of all the students is:
Options:
A) 53.33	B) 54.68	C) 55	D) 56.09	E) None of these
Explanation:   Required average = (55 × 50 + 60 × 55 + 45 × 65/55 + 60 + 45)   = (2750 + 3300 + 2925/160)   = 8975/160   = 56.09   Answer: 56.09
<result>D</result>
If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 65, then the average marks of all the students is: