The price of a BKV student monthly ticket is $465 \mathrm{Ft}$. A 4-month discounted ticket, which can be purchased in September, costs $1700 \mathrm{Ft}$. A bank offers a monthly interest rate of $2 \%$ to depositors. Pisti bought the discounted ticket. Gyurka pays for the ticket monthly, keeping the remaining amount from the $1700 \mathrm{Ft}$ in the bank. Did Gyurka make a good decision?
In the first month, Gyurka pays off his rent and puts the remaining money, $1700-465=1235$ Ft, into savings. By the end of the month, he will have $1235 \cdot 1.02=1259.7 \mathrm{Ft}$.

From this, he pays off his rent again and deposits the remainder back into the bank; and so on, step by step, we can calculate that by the last, that is, the fourth month, he will only have $352.50 \mathrm{Ft}$ left, which is not enough to pay the new rent. Therefore, Gyurka made a poor decision.

Note. With a bit more mathematical knowledge, we can also calculate directly. Let's write a formula to show how Gyurka's money changes from month to month:

$$
\begin{gathered}
(((1700-465) \cdot 1.02-465) \cdot 1.02-465) \cdot 1.02= \\
=1700 \cdot 1.02^{3}-465 \cdot\left(1.02^{3}+1.02^{2}+1.02\right)= \\
=1804.05-1.02 \cdot \frac{1.02^{3}-1}{1.02-1}=1804.05-1451.55=352.5
\end{gathered}
$$

(We used the well-known sum formula for a geometric series. The calculations were performed with rounding to two decimal places.)