Biinkov Add:

A thick issue of the newspaper costs 30 rubles, and a thin one is cheaper. A discount of the same percentage is applied to all newspapers for pensioners, so they buy a thin issue of the same newspaper for 15 rubles. It is known that in any case, the newspaper costs a whole number of rubles. How much does a thin newspaper cost without the discount and how much does a thick newspaper cost for pensioners?
Let the cost of a thick newspaper for pensioners be $30 k$ rubles $(k<1)$, and the full cost of a thin newspaper be $x$ rubles $(x<30)$. Then $k x=15,30 k x=450$. By the condition, $30 k$ and $x$ are integers, so $x$ is a divisor of the number $450=2 \cdot 3^{2} \cdot 5^{2}$, and $15<x<30$. Therefore, $x=25$ or $x=18$.

## Answer

25 rubles and 18 rubles or 18 rubles and 25 rubles.