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© Copyright 1999, Jim Loy
One of my cousin's architecture professors claimed that he was more accurate with a slide rule than anyone could be with an electronic calculator. He marked points off if you disagreed with his slide rule. A circular slide rule was the most accurate (as the outer scales were surprisingly long), and could get no better than 4 digits of accuracy. Electronic calculators routinely get 10 digits of accuracy, then and now. The last digit may be wrong, on some calculations. Rarely, several digits may be wrong on functions like x to the y power.
A friend of mine was asked to factor 6, in his high school algebra homework. He wrote 3x2, which the teacher marked wrong. He had earlier instructed the class to list factors from smallest to largest. So, 2x3 was the correct answer. Now, I see his point. But I object to marking 3x2 completely wrong. Some partial credit seems better, to distinguish 3x2 from a totally incorrect answer like 3x4.
In my article on pi, I mention this story: A mathematics teacher (in High School, as I recall) told us that pi was exactly 22/7 (3+1/7), which is 3.142857142857142857... Not bad (3 digits of accuracy), but certainly not exact. More accurately, pi is about 3.14159 26535 89793 23846...
Teachers are people, and they make mistakes. Most of them will admit the mistake, and correct the grade.