1 mentioned in the title, take out a net, in which 150 fish are unmarked and 4 fish are marked, that is to say, 4 of 154 fish are marked.

2. Assuming that each net is fished out according to the same quantity and proportion, and the marked fish is 100, then a * * * can fish out 100/4=25 nets.

3. Take out 154 pieces at a time, 154*25=3850 pieces.

Formula: 154* 100/4=3850.

So the answer is: there are about 3850 fish in this fish pond.

The calculation method of the first two friends is only the total number of unlabeled fish, without considering 100 tagged fish.

First hit, hope to adopt it in time ~