A woman has six glasses arranged so that three are full and three are empty. The challenge is to make them alternate full, empty, full, empty, full, empty while moving only one glass.
Answer: Pick up the second full glass, pour its contents into the second empty glass, then put the glass back in its original position.
Only one glass has been physically moved. After the liquid is transferred, the original sequence changes into an alternating pattern of full and empty glasses.
The trick is realizing that “move one glass” does not mean you must relocate it permanently—you can use the one moved glass to transfer the liquid.
