Question

in a school 35 boys and 85 girls appeared in an examination.the mean marks of boys was found to be 40%, where as the mean of girls was 60%.determine the average marks % of the school.

Answer 1

According to question

Number of Boys  = 35
Number of Girls = 86

Let total Marks of Boys be X
and Total Marks of Girls be Y

Thus According to question
X/35 = 40
X = 35 * 40
X = 1400
And 
Y/85 = 60
Y = 5100
Thus Total Marks = X + y = 1400 + 5100
                                         = 6500
Thus average marks = 6500 / 120
                                  = 54.16%

Answer 2

Number of Boys=35
Mean marks of boys=40
Mean marks of boys = sum of marks of boys/total number of boys
sum of marks of boys=35x40=1400

Number of girls =85
mean marks of girls=60
Sum of marks of girls=85x60=5100

Total marks secured by 120 students =1400+5100=6500
average marks of school=Total marks/ number of students=6500/120=54.16

∴The average marks % of the school is 54.16%