A mad scientist has captured you and is showing you around his foul-smelling laboratory. He motions to an opaque, formalin-filled jar. "This jar contains one organ, either a kidney or a brain," he cheerily informs you. His voice seems an octave too high as he gives you a twisted leer. You watch as the madman grabs a brain lying on his worktable and drops it into the jar as well. He then shakes the jar and quickly withdraws a single organ. It proves to be a brain. He turns to you and says, "What is now the chance of removing a kidney?" Fearing that the scientist might remove your kidney in his next ghoulish experiment, you want to give him the right answer. What is your response? (Enter the probability as a fraction.)