Introduction: Napier's Rods
John Napier invented his abacus rods in the early 17th century. Among other things, Napier's Rods can be used for multiplying two factors, and is an ingenious way to multiply multi-digit numbers.
Step 1: Materials
You'll need about a dozen craft sticks, a ruler, a pencil, and some other markers if you want to gussy up your sticks.
Step 2: Make Your Mark
Start by measuring and marking half-inch increments on the craft sticks. I keep extra space at the top. First, make a guide rod, which makes the first column, and is composed of digits one through nine.
Step 3: More Lines
For all the digits zero through nine, make diagonal lines on the sticks from the top right to the bottom left.
Step 4: Complete Your Set
You will then construct a times table for each digit. Multiply the stick's number -- the number at the top -- by the number on the guide stick to the left.
You can make as many sticks as you want, especially if you want to multiply pi to 12 places. If you do have duplicate digits in a factor, make sure you have enough rods. You can always use the back of a stick.
Step 5: How to Use Them
Step 6: Further Exploration
How is the lattice method different from standard multiplication? Is it just a different way to project the carried digit? Can you make binary base rods? Joshf made four-sided Napier's Bones. Can you make these with chicken bones? You could print the rods and paste them on to foam core. Here's a set of rods my wife made on a laser cutter -- for my birthday!
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