Archive | Mental Math

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 […]

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 […]

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.