¿Cuánto es el 21% de 25?

The 17th-Century Tax Crisis

An 18-year-old French math prodigy named Blaise Pascal grew tired of watching his father labor over grueling, manual tax bookkeeping. To solve the problem, he invented the Pascaline—the world's first operational mechanical calculator. It executed addition and subtraction using a complex internal system of interlocking clock gears and brass wheels, hand-turned via a metal stylus.