To me, one of the most stupid ideas in math is the reciprocal.
Even its definition, a number that when multiplied by another number equals one, makes no sense.
Ironically, the number 1 is its own reciprocal in a mathematical version of the song “I’m My Own Grandpa”. I never saw the need for knowing reciprocals except that they help solve math problems in some way that I still don’t understand. My life was perfect without reciprocals until I moved to a cold-weather climate. My heating costs were costing me a fortune and I was faced with the task of insulating my attic. So, I had to figure out how to get an “R” factor of 50. The R factor is used to measure the thermal resistance of most insulations. It is based on two other numbers called the K factor for thermal conductivity and the C factor for thermal conductance and is measured in “R” per inch. But then I began to tremble with fear when I was told that R multiplied by C was equal to 1 meaning that they were evil reciprocals! After several hours of struggling with the equations, I finally did what I should have done at the start and called my friend George, who sells insulation and is not baffled by reciprocals. He calmly explained that if I needed an R factor of 50, simply divide that by the R factor per inch printed on the package. If the R on the package says five, he explained, then 50 divided by 5 is equal to 10 inches thickness of insulation. Sometimes we all need a guy like George.