ALL

Chapter Seven - Performing Basic Calculations with Your Slide Rule 39How to Use a Slide Rulefor Basic CalculationsMultiplicationThe C and D Scales (and the Cl Scale)(and CF & DF and A & B scales)Start with a simple example: 2 X 3 = ?Pickett N-6OOT, 12.5 cmscales, aluminum,duplex, USAMove the slide until the left index of scale C aligns with 2 on scale D.Move the cursor until the hairline is on 3 of scale C.Read 6 at the hairline on scale D.In slide rule language, we would writeLeft index of C to 2 on DCursor to 3 on CAnswer: 6 on D at cursorWhy does this work? What we really did was to take the distance representedby the logarithm of 2 (log 2), and added the distance represented by thelogarithm of 3 (log 3). Log 2+ log 3 = log (2 X 3) = log 6, and log 6 is representedby 6 on the D scale.Even though the numbered locations on the scales are the locations of thelogarithms of our numbers, they are labeled with the actual numbers themselves,enabling us to read our answers directly.Now try: 6 X 7lf we slide the left index of C to 6 on D, we see that 7 on scale C is off theend or “off scale”. So we “switch indexes”...Right index of C to 6 on DCursor to 7 on CAnswer: 42 on D atcursor