A school has 4 sections of Chemistry in Class X having 40, 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.

Total marks obtained by all the students in 1st section = 40 x 50 = 2000.

Total marks obtained by all the students in 2nd section = 35 x 60 = 2100.

Total marks obtained by all students in 3rd section = 45 x 55 = 2475.

Total marks obtained by all students in 4th section = 42 x 45 = 1890.

Overall average of marks per student = Total marks of students of all sections/ Total number of students of all sections

$$\Rightarrow$$ (2000 + 2100 + 2475 + 1890)/ (162) = 8465/162 = 52.25

Hence, option B is the correct answer.