in a school there are three only three sections ABC average marks per student in section A is 72 average marks per student in section b is 77 average marks per student in Section C is 81 of the ratio of the student In these 3 classes is 5:7:9 then what is the average marks per student in the complete school

• Avg=sum Of observation /no of observation.. As
  Sum of observation is 72*5x+77*7x+81*9x=1628x
  Total no of observation is 5x+7x+9x=21x
  So avg =1628x/21x=77.52
  So 77.52 is answer
• 6 years agoHelpfull: Yes(31) No(2)
• Avg=sum Of observation /no of observation.. As
  Sum of observation is 72*5x+77*7x+81*9x=1638x
  Total no of observation is 5x+7x+9x=21x
  So avg =1638x/21x=78
  So 78 is answer
• 6 years agoHelpfull: Yes(3) No(10)