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The magician hands the spectator a pair of scissors and asks her to cut a rope in half.
The spectator fails to open the scissors. She applies all her strength but is unable to separate the blades. The magician takes the scissors and without any effort cuts the rope in half.The magician immediately opens the scissors without any additional effort. He now separates the blades and hands the scissors to the spectator. But now he cannot cut the rope as he fails to close the scissors,

Finally, the magician takes the scissors and cuts the rope.