The Slide Rule-Multiplication
and Division
The fallowing method of learning to use the slide rule applies equally well to both straight and circular slide rules. The use of "upper scale" refers to " C scale on straight slide rules and the "D" or outer scale on circular slide rules. The lower scale is the "Dmscale on straight rules and the "C" scale or inner scale on circular slide rules. Problem 1 . 2 x 3 can be written as 2 x 3 = X or dividing both sides of the equation by 3,
X 2 = 1 3 Place "2" on the upper scale aver "1" on the lower seale and the answer 16) is on the upper scale over "3" on the lower scale. Problem 2. (3.36 X 6.35)/2.32 can be rearranged to read -
3.36 X - - 2.32 6.35 Place "3.36" on the upper scale over "2.32" on the lower seale and the answer (9.2) is on the upper scale over "6.35" on the lower seale. Essentially all problems involving multiplication, division, and combinations of the two as in Problem 2 above can be solved with the slide rule where the work can be expressed as a n equation. The numerators will be on the upper scale and the denominators will be on the lower seale.
Moses Brown School Providence, Rhode Island 02906
Volume 51. Number 8. August 1974
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