In a class of 100 students there are 70 boys whose average marks in a subject are 75. If the average marks of the complete class is 72, then what is the average of the girls?
Solutions · 1
Official solution
Total marks of class =100×72=7200. Total marks of 70 boys =70×75=5250.
Total marks of 30 girls =7200−5250=1950
\[\text{Average of girls} = \frac{1950}{30}=65\]