I was first stumped by how to get two jugs each filled with 1 liter of water. I tried doing it in my head without much luck.
So I went the slow methodical approach of writing every step on paper. I even had to figure out how to display my steps since the jugs have numbers associated with them for their total volume (2,4,7,9) and each step changed the amount of water in a vessel.
I also realized that adding two arrows ⬇️↘️ helped to show when only part of the water in a vessel was poured into another.
When I realized I could get 4 liters into 2 vessels and then end up with the “second 1 liter” if I filled up the 7 liter vessel, it was pretty much solved.
I don’t think I duplicated any steps with my approach, just took a longer path.
But asking can I do it in fewer steps should have been the next question.
I guess the next questions after that is
What is the volume ratio of vessels required to have 5 liters in 3 vessels? 7 liters in 3 vessels? n liters in 3 vessels?
Does the ratio need to change if you have even liters in 3 vessels? I.e. 4 liters in 3 vessels? 8 liters in 3 vessels?