The average marks of boys in a class is 52 and that of girls is 42. The average marks of boys and girls combined is 50.What is the percentage of boys in the class ?

• let percentage of boy is p% and girls is (100-p)%
  52p+42(100-p)=50*100
  p=80
• 12 years agoHelpfull: Yes(3) No(0)
• using allegation and mixtures,
  
  52 42
  50
  50-42 52-50
  =8:2=4:1
  
  boys%=4/(4+1)*100=80
• 12 years agoHelpfull: Yes(2) No(0)
• let no. of boys=Nb no. of girls=Ng
  marks of boys=Mb marks of girls=Mg
  Total marks of class=Mb+Mg
  1. Mb/Nb=52 2. Mg/Ng=42
  3. (Mb+Mg)/(Nb+Ng)=50
  52Nb+42Ng=50Nb+50Ng
  therefore Nb=4Ng
  
  for % of boys Nb/(Nb+Ng)*100
  4Ng/(4Ng+Ng)*100
  4/5*100= 80
• 10 years agoHelpfull: Yes(0) No(0)