2. Fishermen caught 80 fish in a pond with a net, marked them, and released them back into the pond. The next day, they caught 150 fish, 5 of which were marked. How many fish are there in the pond in total?

Note. The marked fish are evenly distributed among the others.
2. Obviously, the marked fish mixed uniformly with all the fish in the pond. Among the caught fish, the marked ones constitute $5: 150=\frac{1}{30}$. Therefore, the total number of fish in the pond is $80 \cdot 30=2400$ (fish).