How to Figure Averages with The Top of A Shoe Box; or the Use of an Alignment Chart in Averaging
J. A. Roberts · Mathematics Teacher Learning and Teaching PK-12 · 1924
We have all admired the slide rule as a device for multiplying and dividing, squaring, cubing, and taking roots with a minimum expenditure of brain energy on our part. There is something attractive in manipulating a mechanical device and producing a result automatically. It is too bad that a slide rule will not add and divide so as to figure our averages for us; but add it certainly will not.