The ratio of the number of boys and girls in a college is 7 : 8. If the percentage increase in the number of boys and girls be 20% and 10% respectively, what will be the new ratio?
a)8 : 9
b)17 : 18
c)21 : 22
d)Cannot be determined

• 
  The ratio of the number of boys and girls in a college is 7 : 8.
  let number of boys and girls in a college are 7x and 8x.
  After increase no of boys and girls are 7x*1.2 and 8x*1.1.
  
  Ratio is 8.4x : 8.8 x = 21:22 .... option c)
• 13 years agoHelpfull: Yes(28) No(4)
• Let boys=7x and girls=8x
  after increase boys=7x+7x*20/100=42x/5
  girls=8x+8x*10/100=44x/5
  boys:girls=42x/5:44x/5
  =21:22
• 10 years agoHelpfull: Yes(3) No(0)
• Let the numbers of boys and girls are 700 and 800 respectively.
  after increament no of boys and girls will be (700+(700*20%)) and (800+(800*10%)) ie 840 & 880
  
  Ratio=840/880
  And:--21:22
• 10 years agoHelpfull: Yes(3) No(0)
• make ratio 70:80 right, then 14% of the 70 is 14 and 10% of the 80 is 8. so 70+14=84 and 80+8=88 ( beacuse increase). so new ratio became 84:88. now check option one by one that satisfy option C
  
• 9 years agoHelpfull: Yes(0) No(0)
• ans: 21:22
  120% of 7x=120/100*7x=42x/5
  110% of 8x=110/100*8x=44x/5
  42:44
  21:22
• 7 years agoHelpfull: Yes(0) No(0)