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Rotarule Model AA Circular Slide Rule 

  • ca. 1939
  • Manufactured by Rotarule
  • .375 in. H x 6 in. diameter
    Plastic, steel, leather, paper
  • On display in Making Modernity
  • Gift of Dr. Andrew Benson
  • 2006.037.001A-D


A slide rule is a manual calculator used primarily for multiplication and division, although more complicated calculations, such as roots, logarithms, and trigonometry, can be done. The typical slide rule is either linear or circular and has a standard set of scales printed on it. Calculations are performed by arranging the movable scales into the proper position for the necessary calculation. Specialized slide rules were created for a range of professions, including aviation, finance, and navigation, which featured additional scales specific to those professions. The slide rule remained the most popular tool for calculation until the early 1970s when the scientific calculator replaced it.

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