1) In a school with 600 students, the average age of the, boys is 12 years and that of the girls is 11 years.- If the average age of the school is 11 years 9 months, then the number of girls in the school is : A) 150 B) 250 C) 350 D) 450 Answer: Option AExplanation:Let the number of girls be x.Number of boys be 600-x $11\frac{3}{4}\times600=11x+12(600-x)=>x=7200-7050=>x=150$
