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

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the answer is no been given till now why this so .

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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 ×number of girls

=73 × 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 × number of boys

=71 × 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

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