# Slide Rules and Log Scales as a Primer for Reading Graphs

Friday 3:20pm-3:40pm Northrop Hall: 340
Teaching Demonstration Part of Friday Session B

Victor Ricchezza, Georgia State University

### Demonstration

The participants will be given a short primer on the workings of a slide rule. Participants will use 3D-printed logarithmic slide rules made at USF and work in small groups to perform a few calculations ranging from simple multiplication to trigonometry to logarithms. Following the active portion of the demonstration, I will show how students then create their own working slide rules out of log scales, and how we bridge this into reading logarithmic scales on graphs and plots. Ultimately we use this to discuss how modeling functions can be shown to be "linear" on different axis systems once students understand logarithmic scales.

## Abstract

The participants will be given a short primer on the workings of a slide rule. Participants will use 3D-printed logarithmic slide rules made at USF and work in small groups to perform a few calculations ranging from simple multiplication to trigonometry to logarithms. Following the active portion of the demonstration, I will show how students then create their own working slide rules out of log scales, and how we bridge this into reading logarithmic scales on graphs and plots. Ultimately we use this to discuss how modeling functions can be shown to be "linear" on different axis systems once students understand logarithmic scales.

Differences between the demo and our course: the demonstrated dry lab activity with the slide rules is significantly longer in the classroom setting, and time constraints do not allow us to ask audience members to make log scales of their own.

At the end of the activity, participants/students should be closer to quantitative literacy in one primary factor: when they first look at a plot/graph, the first thing they look at should be the axes. This activity reinforces that concept, and has good success in our course.

## Context

Students are led through the uses of logarithmic scales in slide rules, then asked to create their own scales and make slide rules from these scales. This is used in conjunction with targeted problem sets in our course. The use of log

## Why It Works

The logarithmic slide rule would probably be better described as anachronistic rather than innovative, but the use of a slide rule makes students think about how answers are obtained rather than trust the magic black box effect inherent in an electronic calculator. Students who have taken our course (computational geology) have a tendency to look at graphs correctly - first at the axis, then the labels, then lastly at the plotted data - and this indicates at least anecdotally that this seems to work.

#### Presentation Media

The following are are .stl files for 3D printers. After downloading the file, you will need to edit the file name to add the .stl extension so your computer recognizes it.