Let X and Y denote the sets containing 2 and 20 distinct objects respectively and F denote the set of all possible functions defined from X to Y. Let f be randomly chosen from F. The probability of f being one-to-one is ______.
GATE 2015 · Discrete Mathematics · Functions · medium
Answer: 0.95
Count total functions from X to Y: Total functions = 20^2 = 400
Count injective functions from X to Y: Injective functions = P(20, 2) = 20 * 19 = 380