overall: 4.1 cm x 217 cm x 22 cm; 1 5/8 in x 85 7/16 in x 8 11/16 in
United States: New Jersey, Hoboken
This is a one-sided 79-inch demonstration slide rule from 1967. It is made of painted wood, with a plastic cursor that has a wooden frame. In the early seventeenth century, the Scottish mathematician John Napier discovered functions known as logarithms which make it possible to reduce problems of multiplication, division, and taking the roots of numbers to additions and subtractions.
On a slide rule, the logarithms of numbers are represented as lengths. To multiply, one length is set on the base, and another added to it using the slide. The sum of the logarithms, which gives the product, is read off using the cursor. This slide rule also has scales for finding the squares, cubes, square roots, and cube roots of numbers.
Slide rules first became popular in the United States in the 1890s, especially among engineers and scientists. Use of the device was taught in high schools and universities using oversized instruments like this. During the 1960s, the United States placed new emphasis on teaching mathematics and science. This slide rule was purchased and used at a high school for girls in Pittsburgh, Pennsylvania. By the late 1970s, slide rules would be almost entirely displaced by handheld electronic calculators.