5. A group of third-graders decided to go on a trip to Moscow on March 19 after a math olympiad. Each student contributed the same amount of money monthly, and over 9 months, they collected 22725 rubles. How many students were in the class and how much did each student contribute monthly?
5. 6) $22725: 9=2525$ (rubles) — the amount the students paid for one month.

To determine how much each student paid monthly, we need to know the number of students in the class. This is unknown in the problem. However, from the problem's condition, it follows that this is a natural number that is a divisor of 2525.

$$
\begin{gathered}
2525: 5=505 \\
505: 5=101
\end{gathered}
$$

Thus, there could have been 5, 25, or 101 students in the class. Since it is impossible to have 101 students in a class, the number of students was either 5 or 25.
2) $2525: 5=505$ (rubles)
3) $2525: 25=101$ (rubles)

Answer: 5 students paid 505 rubles each or 25 students paid 101 rubles each.