To add fractions with unlike denominators, students have to first write equivalent fractions that have the same denominator. One strategy is to multiply both parts of the first fraction by the other denominator and then multiply both parts of the second fraction by the first denominator. For example, to add 2/5 + 3/8, students convert them to equivalent fractions with 40 as a denominator; 16/40 + 15/40. The sum is 31/40. Sometimes, however, one denominator may be a multiple of the other. In cases like this, simply express the other fraction as an equivalent fraction with the denominator that is the multiple; for example, 2/8 + 7/24 becomes 6/24 + 7/24.
This PowerPoint lesson is a multi-click animation sequence that introduces standards-based math skills and concepts. Also includes three practice pages at levels A (below grade level), B (at grade level), and C (above grade level), which may be distributed according to students' abilities!