$4 \cdot 227$ A person spent one coin to buy a loaf of bread and a bottle of kvass (a drink). When prices increased by $20 \%$, the coin was only enough to buy half a loaf of bread and a bottle of kvass. Question: If prices increase by another 20%, will the coin be enough to buy just a bottle of kvass?
[Solution] Let the coin value be 1. Before the price increase, the price of a loaf of bread is $x$, and the price of a bottle of kvass is $y$. According to the problem,
$$\left\{\begin{array}{l}
x+y=1 \\
1.2(0.5 x+y)=1
\end{array}\right.$$

Solving these equations, we get
$$y=\frac{2}{3} \text {. }$$

Since $\frac{2}{3} \cdot 1.2 \cdot 1.2=\frac{2}{3} \cdot \frac{6}{5} \cdot \frac{6}{5}=\frac{24}{25}<1$,
therefore, after the prices increase by another $20 \%$, the coin is still enough to buy a bottle of kvass.