This activity uses unit squares to help students investigate addition and subtraction of fractions with unlike denominators.

This TI-Nspire™ lesson uses unit squares to help students investigate addition and subtraction of fractions with unlike denominators. Students should recall that only fractions with a common denominator can be added. So, they can use their prior knowledge to add fractions with unlike denominators by finding a common denominator. Note that the objective is to develop a simple, generalized method for finding the sum of two fractions. Finding a least common denominator is not necessary and, in fact, can lead to confusion for students, obscuring the goal of adding fractions. The files can also be used to investigate the properties for addition (commutative, associative, identity, inverse).

Students should be familiar with the terms unit fraction, equivalent fraction, common denominator, improper fraction, tiling, and unit square covered in earlier activities.

This is Lesson 7 out of 15 in the Building Concepts in Mathematics: Fractions Series.

Standards