Brahmagupta’s Rules for Multiplication and Division of Positive and Negative Numbers

Transcript

Brahmagupta’s Rules for Multiplication and Division of Positive and Negative NumbersThese are also called Brahmagupta's "Money Rules" Brahmagupta was one of the first people to write down the rules for positive and negative numbers. He used words that are easy to picture: Fortune (Dhana): Money you have (Positive Number, +) Debt (Rna): Money you owe (Negative Number, -) His rules translate exactly to the math rules we use today: "Product of two fortunes is a fortune" → Positive × Positive = Positive "Product of two debts is a fortune" → Negative × Negative = Positive "Product of a debt and a fortune is a debt"→ Negative × Positive = Negative "Product of a fortune and a debt is a debt"→ Positive × Negative = Negative And, these are also valid for division ”Quotient of two fortunes is a fortune" → 𝑃𝑜𝑠𝑖𝑡𝑖𝑣𝑒/𝑃𝑜𝑠𝑖𝑡𝑖𝑣𝑒 = Positive "Quotient of two debts is a fortune" → 𝑁𝑒𝑔𝑎𝑡𝑖𝑣𝑒/𝑁𝑒𝑔𝑎𝑡𝑖𝑣𝑒 = Positive "Quotient of a debt and a fortune is a debt"→ 𝑁𝑒𝑔𝑎𝑡𝑖𝑣𝑒/𝑃𝑜𝑠𝑖𝑡𝑖𝑣𝑒 = Negative "Quotient of a fortune and a debt is a debt"→ 𝑃𝑜𝑠𝑖𝑡𝑖𝑣𝑒/𝑁𝑒𝑔𝑎𝑡𝑖𝑣𝑒 = Negative