Spice Problem Activity

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SWBAT use their knowledge of adding and subtracting fractions.

Big Idea

Students will mix spices to understand fraction concepts.

Do Now

10 minutes

Students previously worked on developing algorithms for adding and subtracting fractions.  Students had difficulty with subtracting mixed numbers, especially when the fraction part of the minuend was smaller than the fraction part of the subtrahend.  The Do Now is an assessment of students' ability to recognize a common mistake in subtracting mixed numbers and to correct the mistake.

For the Do Now, students will be given the attached problem with the following directions.  Subtracting Mixed Numbers Do Now

Find and explain in words the errors being made.  Then solve the problem correctly.


Those students who have difficulty with this concept, may not see the error.  Is 5 - 9 the same as 9 - 5? I will remind them to look at the algorithms and examples we've previously worked on.



Group Activity

30 minutes

This is a student centered activity designed by the CMP3 Mathematics program.  I am using it to reinforce students' skills of adding and subtracting fractions/mixed numbers and to continue with a real world application of these skills.

Students will be given the Spice Problem Worksheets.  We will read through the introduction together and I will ask some initial discussion questions.  Which recipe uses the most cinnamon?How can we compare the different amounts of cloves used in the recipes? About how much more does one batch of Betty's Cake Spices weigh than one batch of Garam Masala?

Students are seated in groups of four, with at least one high level math student in each group.  Because I don't want the high level student to dominate the discussion, I will explain that this is a collaborative activity.  Each student should share their ideas and strategies with the group.  They should all agree on the answer.  If students do not agree on an answer, they should discuss their work.

As students work I will circulate throughout the class, look for different strategies that students use, and clarify any confusion.

Students may have questions concerning A.2.b and B.2.b..  These sections ask them to show a way to determine the answer using subtraction.  However, students may have already used a subtraction strategy for section a.  I will explain that if that's the case, they should find another strategy for determining the answer.

Students will have 25 - 30 minutes to work on the activity.  If they don't finish the activity with their group, they will complete it for homework.

Lesson Review

5 minutes

Most groups may have not completed the activity, so I will not review the answers.  I will discuss the different strategies they may have used.

- What denominator did you use in the Spice Parisienne problem?

- What tells you the problem requires adding?

- What are some strategies you found useful when combining or adding quantities of spices?