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Here is a variant of the three utilities puzzle. Famously, It is impossible to solve it on a plane paper (Euler's theorem can prove that). But can you solve it on a coffee mug?

Connect all three utilities to each of the houses, such that no two lines intersect.

Don't draw on the inside, It's for drinking ofcourse.

enter image description here

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  • $\begingroup$ There seems to be a conflict between not citing the source of this puzzle, and the spam policy. However, since I think there are very few of us here who wouldn't want to enjoy their coffee made with well connected heat, electricity and water, here's the link: mathsgear.co.uk/products/utilities-puzzle-mug $\endgroup$
    – Bass
    Dec 25, 2017 at 12:38
  • $\begingroup$ @Bass, I saw these mugs with one of my colleagues. So I didn't knew if they were mass produced. I will add it to the question. No worries. $\endgroup$
    – prog_SAHIL
    Dec 25, 2017 at 12:59

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When trying to connect all utilities $A$, $B$ and $C$ to the three houses one realizes that

one needs just 1 "crossing" of lines (see drawing). This can be done on a topology like a mug (or donut) by having one of the lines going on the handle of the cup and the other one through it.

And this is how it looks like on a cup:

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Yes, you can, just...

use the handle to jump over a line you would have to cross on a plane.

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