A school has 4 section of Chemistry in Class X having 50, 35, 45 and 42 students. The mean marks obtained in Chemistry test are 50, 60, 55 and 45 respectively for the 4 sections. Determine the overall average of marks per student.
Choose the correct choice
A) 50.12  B) 52.12  C) 51.12  D) 53.12  E) none of the above

Rationale: "required average marks = 50 ã — 50 + 35 ã — 60 + 45 ã — 55 + 42 ã — 45 / 50 + 35 + 45 + 42 = 2500 + 2100 + 2475 + 1890 / 172 = 8965 â  „ 172 = 52.12 answer b"
Answer: B