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Digital Root

By Kardi Teknomo, PhD.

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One day I talked about recognizing patterns from numbers, many students just stared at me with blank face. When I introduce digital root or digit sum to them, their puzzling faces suddenly disappear. They could recognize the pattern easily, even the younger one. Some are actively pursue their own discovery on mathematical pattern.

The idea of digit sum or digital root is very old but it is very interesting. It is a mind exercise to guide students discovers patterns and simple formulas by themselves. This kind of exercises does not require high mathematical knowledge (basically, only addition and multiplication); instead it will serve as a mean for mathematics teachers to support the students to explore fascinating pattern and the beauty of mathematics.

In this tutorial you will learn about (click the following topics):

Significant of digital root (motivating examples)
Guess a Hidden Digit
Digital root of Fibonacci
What is Digital Root?
Understanding Pattern of Digital Root
One Dimensional Pattern of Digital Root
Diagram of Digital Root Pattern (interactive program)
Two Dimensional Pattern of Digital Root
Arithmetic of Digital Root
Vedic Square
Making Vedic Square using Matlab
Group of Digital Root
Power of Digital Root (interactive program)
Power Digital root code in VB (MS Excel Macro)
Digital root of prime numbers

Preferable reference for this tutorial is

Teknomo, Kardi (2005). Digital Root. http:\\people.revoledu.com\kardi\tutorial\DigitSum\

(last updated: October 2011)