y as a percentage of x is the same as x as a percentage of (x + y). Find the numerical value of y as a percentage of x.

1) 73
2) 34
3) 62
4) 57

• 3) 62
  Given y*100/x=x*100/(x+y) =>x^2-y^2-xy=0
  Dividing above eqn. by xy we have x/y -y/x -1=0
  As we want ratio y/x, replace term y/x by z, we have 1/z -z -1=0
  z^2+z-1=0 => z=[-1+sqrt(5)]/2=(-1+2.236)/2=0.618~ 62%
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