A mixture of $$N{H_4}N{O_3}$$   and $${\left( {N{H_4}} \right)_2}HP{O_4}$$    contain $$30.40\% $$  mass per cent of nitrogen. What is the mass ratio of the two components in the mixture?

Solution :
Let $$wt.$$  of $$N{H_4}N{O_3}$$   and $${\left( {N{H_4}} \right)_2}HP{O_4}$$    are $$x$$ and $$y$$ gram respectively
$$\eqalign{ & \frac{{\frac{x}{{80}} \times 2 \times 14 + \frac{y}{{132}} \times 2 \times 14}}{{x + y}} \times 100 = 30.4 \cr & \Rightarrow x:y = 2:1 \cr} $$