Solution to Puzzle #164: The Physics Puzzle

I am posting the solution for Puzzle #164 before I do so for puzzle #163, which I will do next week. It was not too difficult a puzzle, and even if you did not try it with your children, please do so again, it will be fun. Thanks to many of you for correct answers – Pratik Poddar, Vishal Poddar, Prakhar and Sid Mulherkar. For a change, I also did the puzzle correctly 🙂

The answer is that 3&4 will be full together. Lets see it with the help of the following diagrams (entire answer copied from quora at

It is simple Fluid Dynamics. Let’s do it on Paper assuming ideal condition. Keep imagining to understand.

  1. We have 1 water outlet & 4 tanks connected to each other as shown in picture.

2. Open valve, Tank-1 will be filled as shown below.

3. Now T1 level_constant & T2 level_increase

4. T1,T2 level_constant & T3 level_increase

5. T1, T2 level_constant & T3 level is increasing.


7. Now water will flow to T4.

T1, T2, T3 level_constant & T4 level_increase.

8. T1, T2, T3 level_constant & T4 level is increasing.

9. T3 = T4.

10. Now T2, T3, T4 level increase with same value.

11. T3 & T4 is completely filled.

Infinite condition all tank level constant. Water given to T1 will be totally spill out by T3 & T4.

*Ideal condition means all tanks & pipe connection are same, Room temperature-pressure, Fluid used water, No any type of losses, water flow at constant pressure-value, and “neglecting your high intelligence :P”

Hope you all enjoyed the puzzle.

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