Archive | Number Theory

GCF of 2 Numbers, Trick Finds it Fast

Ever need to find the GCF of two numbers? Here’s a trick for finding the GCF of any two numbers — very quickly. This is an original trick, so I doubt you’ll find it anywhere else online. But most important, it’s easy to use, and it works no matter how large the numbers might be. Also nice … learning this […]

The GCF (aka GCF) … what is it?

The GCF is the greatest common factor, and it’s a key concept in math. This term is also known as the GCD, the greatest common divisor. Students often need to find this quantity either for a pair of numbers or for three or more numbers. For example, knowing the greatest common factor allows students to reduce […]

Journey to the LCM … and Beyond!

In this blog/video I want to take you a little bit deeper into the world of … the LCM! Yes, that fascinating little mathematical entity is beckoning us to explore it further. Several readers wrote to me after I posted my LCM “trick,” saying they want to see me demonstrate WHY this “shortcut” works. One […]

Problem of the Month – January 2013

Twelve is the first number with two pairs of factors (2 x 6 and 3 x 4). Primes, on the other hand, have no pairs of factors other than the trivial pair of one and the prime number itself. Considering that contrast, here’s an interesting fact about primes and the number 12. Add 12 to […]

The “Ladder of Primes”

Prime numbers help us reduce fractions Using the “Ladder of Primes,” students can more easily and more quickly reduce fractions to lowest terms.

Quick Easy Way to Untangle Confusion re: “Greater” and “Less”

Once students learn about negative numbers and absolute value, the concept of greater and less becomes a bit “cloudy.” What was once clear is now “muddied.” But there is an easy way for students to tell which of two numbers is greater and which is less. That method involves looking at the numbers on the […]

Secrets of the Calculator, Part 2

Calculators are designed to make it easier to input mathematical expressions. The EE key makes it easy to input scientific notation terms. This post explains how to use the key to make it a breeze to input scientific notation.

Secrets of the Calculator, Part 1

Calculators can be great assistants when doing math. Unfortunately many students are unaware of the capability of many calculator keys. This is the first in an occasional series of posts that will help students learn how to make better use of the calculator.

How to See Why the Divisibility Trick for 3 Works

There’s a nifty trick for finding out if 3 divides evenly into a number. This little proof shows why the trick works.