Originally Posted by henke37
I never understood this one, even after reading the how.
1. You can see 10 fish in the image, meaning there must be a total of 19 fish since there's a key in one of them.
2. Since there are 4 red fish, and you know it's the least numerous, there has to be 5 of each of the other kind, and since you see all of them, it's got to be on the top of the food chain.
3. The green fish can't be next on the food chain, since there's only two missing, and the red fish can max hold three fish + a key. If the tiny tanfish is next on the food chain, it means the four missing are inside the red fish, but then only 1 tanfish can have eaten another fish, and there are 2 green and 3 blue fish missing.
4. This means the blue fish is on the next rung, and since only 3 are missing, it must mean that the key is in one of the red fish.
5. There's only one line with a red fish where there can be a total of 5 fish.