Math Concepts: Adding Fractions; Like and Unlike Denominators; Equivalent Fractions

What You Can Do: Students can learn about adding fractions in a variety of ways. One method is to use models such as fraction strips. Each fraction strip is divided into equal sections. The total number of sections represents the denominator. The number of shaded sections represents the numerator.

For example, a fraction strip for 2/3 has three equal sections (each is one-third) and two of these sections are shaded. If the area of the shaded portion of two fraction strips is the same, the fractions are equivalent.

To add fractions using fraction strips, simply add the shaded portions. To name the result, you may need to change the way the fraction strips are subdivided.

Another method for adding fractions is to write an expression and simplify it. To add fractions with like denominators, you can simply add the numerators while keeping the denominator the same.

To add fractions with unlike denominators, first find a common denominator. Then use this denominator to write equivalent fractions. An easy way to find a common denominator is to multiply the denominators. For example, to add 1/4 + 1/3 , first convert each fraction to twelfths because 4 × 3 = 12, and then add the numerators.

Multiplying by 3/3 or 4/4 is the same as multiplying by 1.

Now the denominators are the same, so add the numerators.

Math in the Game: Players quickly learn to look at the unshaded parts of target fractions to see what they need to make a sum of 1. After a while, players may start to “think in twelfths” because all fractions in the game can be renamed with 12 as a denominator. Using a common denominator is particularly useful for finding ways to make a sum of 1 using two or three bars.

Related Resources:

Fraction Model II

Students can select “Rectangle Model” and use the area models to find equivalent fractions.

Fraction Game

Students can practice working with relationships among fractions and finding different ways to combine fractions.