Tag Archives: fractions

Adding Fractions: Why Avoiding Common Denominators Works

I wrote this post showing that adding fractions can be done using the algebraic definition of addition of rationals: MathHeadInc (via twitter) has requested a video showing why this works. I aim to please. Here is the video showing why adding fractions using a common denominator is the same as the definition of addition of… Continue Reading →

How to Never Find a Common Denominator Again

Do you keep struggling to teach common denominators? Do your kids just not “get it”? Well, it’s time to quit. Yep! You can teach (and do) fractions without ever finding a common denominator. The key is in the definition of addition for rational numbers. If you have two numbers  and  the sum of them is . Granted… Continue Reading →

How to Use Prime Factors to Cancel Fractions

I previously posted about prime factors and about using them in multiplication. Now we’ve got fractions to handle. Before we get in too deep, first let me note the main reason why we do this with arithmetic. In algebra, students will be asked to take a rational expression, factor it and reduce it like this:… Continue Reading →