Solubility of urea in water
Well, that is just the way that it is...

You should also look at this a bit differently. Urea has a molecular weight of 60 and water has a molecular weight of 18. 

$\dfrac{108}{60} = 1.8$ moles urea

$\dfrac{100}{18} = 5.6$ moles water

$\dfrac{5.6}{1.8} = 3.1$ molecules of water for every molecule of urea