How Brahmagupta wrote the sign rules for multiplying and dividing in 628 CE, using fortunes and debts.
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Brahmagupta's four rules as he wrote them.
How an Indian mathematician wrote the sign rules about 1,400 years ago.
Brahmagupta wrote down rules for adding and subtracting positive and negative numbers. In his book Brāhmasphuṭasiddhānta (628 CE) he also wrote clear rules for multiplying and dividing them.
He called a positive value a fortune (dhana) and a negative value a debt (ṛṇa).
Brahmagupta writing his rules in 7th-century India.
Brahmagupta called a positive number a fortune (dhana) and a negative number a debt (ṛṇa).
Turning each fortune-and-debt line into a multiplication.
Problem. Write one multiplication example for each of Brahmagupta's four rules.
Match each fortune-and-debt phrase to its sign rule and example.
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Definitions
Decide whether each product or quotient is a fortune or a debt.
is…