Riddles, brain puzzles and mathematical problems

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Next question:



This crudely drawn circuit has 3 switches on top and 2 at bottom. The probability that any switch is open is 1/3.



Find the probability that a current can travel across this circuit.

I don't quite understand the drawing... Is the negative pole supposed to be on the left and the positive pole on the right?
In that case I think one would have to add the probability of the upper line being closed and that of the lower line being closed:

upper line:
2/3 x 2/3 x 2/3 = 8/27

lower line:
2/3 x 2/3 = 4/9 = 12/27

makes 20/27 or ~0,740 (period)

Both lines being closed should already be included in that I think...

That seems way too easy though... so I'm probably wrong or I misunderstood something