While doubling a cupcake recipe, students practice three ways of doubling fractions using representations, addition, and multiplication. They also convert between improper fractions and mixed numbers.
Part I: Learning Activity
1. Have the students work in pairs for this activity.
2. Read the following to your students: "In a Cyberchase For Real episode, Bianca is helping a friend bake cupcakes for a party. Bianca's friend is supposed to bake 24 cupcakes, but her recipe only has the ingredients listed for 12, so they have to double the recipe. When you have to adjust the amounts of a recipe, there may be several strategies you can use. In this activity, you will try out ways of adjusting amounts in these recipes and develop your strategies."
3. Distribute Handout 1: Grandma Gittel's Favorite Cupcake Recipe .
4. Ask the students to complete the ingredients list for 24 cupcakes, and fill in the table in Handout 1.
5. Tell the students that they will watch a video clip in which Bianca and her friend try to figure out the amount of ingredients to use to make 24 cupcakes.
6. Play the The Right Amount of Cupcake Mix Video and ask students to write down Bianca's ingredient list as they watch.
7. Ask the students to compare their results in Handout 1 to Bianca's ingredient list in the video clip. Did they notice that they had to double the ingredients before viewing the clip?
8. Tell the students that now that they have doubled the ingredients in the recipe, they will try out three different strategies for doubling.
9. Distribute Handout 2: Three Ways to Double Fractions .
10. Ask the students to complete Handout 2. Encourage them to compare the three methods for doubling as they complete the handout.
11. Tell the students that as they examine recipes, they will find that some ingredients are listed in fractional form. Some of these will be improper fractions, and some may be mixed fractions. Because all these forms are common, they need to learn how to convert them.
12. Distribute Handout 3: Converting Mixed Numbers and Improper Fractions .
13. Ask the students to read and discuss Handout 3.
14. Discuss converting mixed numbers and improper fractions with the students. Make certain that the students understand the distinctions between mixed numbers and improper fractions.
15. Tell the students that doubling mixed numbers is probably easiest if they convert the mixed number to an improper fraction, and then double the improper fraction.
16. Distribute Handout 4: Doubling a Mixed Number .
17. Ask the students to read Handout 4, and complete the problems.
18. Discuss with the students any problems they had in doubling the mixed numbers, or converting mixed numbers to improper fractions, and vice versa.
Part II: Assessment
Assessment: Level A (proficiency): Students are asked to adjust ingredients for 24 and 48 cupcakes from the basic recipe for 12 cupcakes.
Assessment: Level B (above proficiency): Students are asked to double a variety of fractions, and represent them in both numerical form and rectangular graphical representations.
Everyday Math (2004)
Teacher Lesson Guide, pp. 387-397, and pp. 564-621.
Student Reference, pp. 62-78
Math Journal, pp. 198-199, 126-127, 129, 254-55, 269, 275, 277-78
Investigations/Scott Foresman (2006)
Name That Portion
Investigation 2, Sessions 1-9: pp. 32-62