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You are given a rectangular bowl with size 5 x 30 x 40 cm and you should put exactly one liter of water into the bowl. You go to your kitchen, where you can put the water directly into the bowl from the water tap. You have no other tool beside the bowl.

How do you fill the bowl with exactly one liter?

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    $\begingroup$ Is that the internal or external dimensions ? $\endgroup$ – CSM Dec 15 '19 at 22:05
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    $\begingroup$ for simplicity ... the inner dimensions obviously $\endgroup$ – eagle275 Dec 16 '19 at 9:24
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Label one of the bottom corners of the bowl C. Tilt the bowl in such a way that when it is as full as it can be, the water line touches the three corners adjacent to C. This will include the corner directly above C, as well as two corners on the bottom of the bowl.

The volume filled is:

$\frac{1}{6} \times 5 \times 30 \times 40 = 1000cm^{3}$, using for example the expression for volume here.

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