In a class of 100 students, the average amount of pocket money is Rs.35 per student. If the average is Rs.25 for girls and  Rs.50 for boys, then the numberof girls in the class is

Let the number of girls in the class =y∴Number of boys in the class=100-yNow,x  ¯1=25,n1=y,x_ 2=50,n2=100−yAnd,x¯=35, n1+n2=100∴    35=25×y+50×(100−y)100⇒ 3500=25y+5000−50y⇒ 25y=1500⇒y=60∴ Number of girls in the class =60