title: Hindu–Arabic numeral system
context: It was invented between the 1st and 4th centuries by Indian mathematicians. The system was adopted in Arabic mathematics by the 9th century. Influential were the books of Muḥammad ibn Mūsā al-Khwārizmī[3] (On the Calculation with Hindu Numerals, c.825) and  Al-Kindi (On the Use of the Hindu Numerals, c.830).  The system later spread to medieval Europe by the High Middle Ages.
question: When were Arabic numerals adopted in Europe?
answers: High Middle Ages