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Oughtred's Key to Mathematics (1631)

Frank J. Swetz (Pennsylvania State University)

William Oughtred (1574-1660) was an English mathematician and clergyman. In 1631, he published Arithmeticae in numeris et speciebus institutio …, an arithmetic and algebra text which became known as Clavis mathematicae (The Key to Mathematics). This book eventually went through at least seven editions in Latin and English.


The operation of multiplication is considered on page 6. Note the employ of symbolism to denote decimal fractions.


Division is discussed and demonstrated on page 10. Here common fractions are employed.


The content on page 25 concerns algebra.


The example given on page 30: (57209)3 = 187237600770329 may be checked by a modern reader to determine the accuracy achieved.


The images above are provided courtesy of Columbia University Libraries.

For images from a 1667 edition of Clavis mathematicae in Convergence, see Mathematical Treasure: Oughtred's Clavis Mathematicae.

Index to Mathematical Treasures 

Frank J. Swetz (Pennsylvania State University), "Oughtred's Key to Mathematics (1631)," Convergence (April 2018)