The average age of a class is 15.8 years. The average age of boys in the class is 16.4 years while that of girls is 15.4 years. What is the ratio of boys to girls in the class?
(i) 1:2

(ii) 3:4

(iii) 3:5

(iv) None of these

• let x = number of girls
  y = number of boys
  sum of girls ages / x = 15.4
  sum of boys ages / y = 16.4
  The sum of the girls' ages is 15.4x, and boys' sum is 16.4y
  (sum of girls ages + sum of boys ages) / (x+y)= 15.8
  (15.4x + 16.4y) / (x+y) = 15.8
  15.4x + 16.4y = 15.8(x+y)
  15.4x + 16.4y = 15.8x + 15.8y
  0.6y = 0.4x
  0.6y/x = 0.4
  y/x = 0.4/0.6
  y/x = 2/3 which is the ratio of boys to girls
• 11 years agoHelpfull: Yes(9) No(0)
• let ratio of boys:girls=k:1;
  Now (k*16.4)+(1*15.4)=(k+1)*15.8
  implies k=2/3;
  So answer is 2:3
• 11 years agoHelpfull: Yes(1) No(0)