if the average marks of 3 batches of 40 , 50 and 60 students respectively is 45 , 55 , 65 , what is the average marks of all the students ? Select:	A) 56.33	B) 34.89	C) 23.67	D) 54.65	E) 43.98

Rationale: average marks of batch 1 = 45 students in batch 1 = 40 total marks of batch 1 = 40 * 45 average marks of batch 2 = 55 students in batch 2 = 50 total marks of batch 2 = 50 × 55 average marks of batch 3 = 65 students in batch 3 = 60 total marks of batch 3 = 65 × 60 total students = 40 + 60 + 50 = 150 average marks of all the students = ( ( 40 * 45 ) + ( 50 × 55 ) + ( 65 × 60 ) ) / 150 = 169 / 3 = 56.333 answer is a .
Answer: A