An early computing device invented by Reverend William Oughtred in London in the 17th century. Primarily for multiplication and division, the slide rule has two stationary sets and one sliding set of numbers in the center. To multiply, numbers are added; to divide, numbers are subtracted. Subsequent slide rules added scales for trigonometric, powers and root computations.

**Slide Rule and Cursor**

**Multiply 2 Times 3**

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