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 […]

# Archive | Mental Math

# PSAT Math Test, Day of Reckoning … ?

It has finally happened … students have taken the new PSAT. I know because Singing Turtle Tutoring (the tutoring company that my wife and I run) prepares students for this test, and over the last two weeks I’ve been helping many get ready for the new PSAT’s math section. My big word of advice for many students: learn […]

# Find the LCM (aka LCD) in Two Easy Steps

Here’s a quick way to find the Least Common Multiple for a pair of numbers. It involves two short, quick steps: reducing a fraction. Then flipping it and multiplying.

# Find the LCM in a way that makes sense! (Part 2)

Two little exceptions to the technique laid out in yesterday’s post. To make sure you don’t overlook the exceptions, read this post today.

# Find the LCM in a way that makes sense! (Part 1)

For the most part, when you set out to find the least common multiple for a pair of numbers, you are asked to go through a bunch of steps that don’t really make sense. Till now! Here’s a way to find the LCM that truly does make sense. This post explains it in clear English, […]

# 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 […]

# Invisible Misunderstandings: Square roots of 2 and 3

There are large chunks of mathematical knowledge that we often assume students have down. In fact, they often lack that knowledge. A good example is this: most students I work with have virtually no sense as to the value of the square root of 2 or the square root of 3. This post offers a […]

# 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.

# Divisibility by 6: How to find out if 6 divides in cleanly

Learning the rules of divisibility helps all students succeed at math. Learning the trick for 6 is really helpful because it is not easy to see if 6 goes in for most people. This trick makes it much easier to tell.

# How to Find the LCM – FAST!!!

Quick way to find the LCM for any pair of numbers.