a class consist of 50 students out of which 30 are girls . the mean of marks scored by girls in a test is 73 & that of the boys is 71 . find the mean score of whole class .
Number of girls = 30
Mean marks obtained by girls =73
Mean = sum of marks obtained / number of girls (in this case)
Sum of marks =mean x number of girls
=73 x 30 =2190 marks
Total number of students = 50
Number of boys = total number of students – number of girls
=50 – 30 =20 boys
Mean marks obtained by boys = 71
Mean = sum of marks obtained / number of boys (in this case)
Sum of marks =mean x number of boys
=71 x 20 =1420 marks
Total marks obtained by the class =2190 + 1420 = 3610 marks
Mean = total marks obtained by the class / total number of students
= 3610 / 50 =72.2 is the mean