Big Ideas: Because fractions are representations of equal parts, they can only be added or subtracted when those parts are of the same size or value.
This lesson builds on students' work with subtracting fractions with like denominators. This task uses a discussion about sugar content in food and drink. Students determine how much more sugar one item has than another by subtracting fractions with unlike denominators. The mathematical concept in this lesson builds toward future use in solving ratio, rate, and proportion problems, and prepares students for work with greatest common factors and least common multiples in 6th grade algebra.
Vocabulary: area model, numerator, unlike and like denominator, vertical, horizontal, teaspoons
Special Materials:
Colored pencils (optional)
Teaspoon (optional)
Measuring cups (optional)
Sugar (optional)
Lesson plan