Problem of the Day
A new programming or logic puzzle every Mon-Fri

Half Full

You are in an empty room and you have a transparent glass of water. The glass is a right cylinder, and it looks like it's half full, but you're not really sure. How can you accurately figure out whether the glass is half full, more than half full, or less than half full? You have no rulers or writing utensils.

Enjoy your weekend!

P.S. don't drink the water



  • Sam - 3 years, 6 months ago

    Tilt the glass until the water is about to overflow, then look at the bottom corner of the glass opposite where the water is touching the rim. There are 3 possibilities:

    1. You can see the bottom corner - the glass is less than half full

    2. The water line is level with the bottom corner - the glass is half full

    3. You cannot see the bottom corner - the glass is more than half full

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  • Tim at DataRobot - 3 years, 6 months ago

    Beaten by four hours.

    This actually comes in handy all the time. Next time you need to fill the coffee machine's reservoir but it doesn't fit upright in the sink, you can modify this method to make sure you get exactly the right amount of water on the first try by splitting the difference between the water level on the high and low side of the reservoir.

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