If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 70, then the average marks of all the students is:  Options
A) 53.33 B) 54.68 C) 57.5 D) 56 E) None of these
Explanation:   Required average = (55 × 50 + 60 × 55 + 45 × 70/55 + 60 + 45)   = (2750 + 3300 + 3150/160)   = 9200/160= 
<gadget id="calculator">9200/160</gadget>
<output>115/2 = around 57.5</output>
57.5   Answer: 57.5
<result>C</result>
If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 70, then the average marks of all the students is: