Assistant to Scipione dal Ferro (1465-1526), who unwittingly assisted Tartaglia (1499-1557) in learning his master's solution to depressed cubic equations. Before his death, dal Ferro had shown Fior his method for solving the depressed cubic, a cubic equation lacking a second-power term. Up to that point, dal Ferro alone had known the solution, a powerful trump card if he were forced into one of the public mathematical competitions common at the time. As for Fior, he so feared a public challenge that he preemptively approached Tartaglia, giving him 30 problems involving the depressed cubic. As a result, Tartaglia was forced to find the solution, which he did. Meanwhile Fior, who could only answer a handful of the questions put to him by Tartaglia, suffered a humiliating defeat.