Engaging students: Dividing fractions

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for engaging their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Chelsea Hancock. Her topic, from Pre-Algebra: dividing fractions.

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Applications (A1)

Students can encounter the division of fractions in a variety of places outside of the classroom. Some of these instances could even happen in your own home! When using fractions, the most common examples include slicing pizza or pie into equal slices. Here is one of those problems:

  1. Assume you have seven-eighths of a whole pizza left. Three of your friends walk into the kitchen and ask for one-fourth of the whole pizza each. If you wanted to share with your friends, will you have enough pizza for each friend to get the amount they want? (Divide 7/8 by 1/4 and see if it’s bigger than three).

 \displaystyle \frac{7/8}{1/4} = \displaystyle \frac{7 \times 4}{8 \times 1} = \displaystyle \frac{28}{8} = 3 \frac{1}{2}

 It is bigger than three, therefore there is, in fact, enough pizza left for all three of your friends to get the amount they wanted.

Other problems might involve finding a fraction of a fraction of a whole. Here is an example of this:

  1. I have a giant cookie jar with 36 cookies in it. My family comes over and eats some of the cookies. If 1/3 of the cookies are eaten and 3/4 of the eaten cookies had frosting, how many of the eaten cookies had frosting? (Multiply 36 by 1/3 to get 12. Then multiply 12 by 3/4).

 \displaystyle 36 \times \frac{1}{3} = \displaystyle \frac{36}{3} =12

 \displaystyle 12 \times \frac{3}{4} = \displaystyle \frac{12 \times 3}{4} = \frac{36}{4} = 9.

Nine of the eaten cookies had frosting.

green lineCurriculum (B2)

In previous mathematics classes, students have obtained a wide variety of skills which can be used when dividing fractions. These skills include the multiplication of whole numbers, the division of whole numbers, and how to reduce fractions to their simplest form. Dividing fractions is an extension of these skills. It can also be said that students already understand what a fraction is. On a separate note, we will discuss how many students relate to fractions and how they think of fractions when confronted with them.

Many students find fractions difficult and intimidating, often freezing when they see a fraction. Involve more than one fraction in a problem and students will get easily frustrated and give up. This can be caused by the way a student perceives fractions. Many students are taught that a fraction is simply part of a bigger whole number. While this is true, many students lose focus on the big picture and get caught up on the fact that a fraction is less than 1 whole unit. In order to help avoid this, teachers could instead try explaining fractions in a slightly different way: a fraction is just a number written like a division problem. The video found at http://www.youtube.com/watch?v=3xwDryouw6o  can help to provide a more in-depth explanation about this new perspective on fractions.

By thinking of a fraction as simply a division problem, students automatically incorporate their previous knowledge on dividing whole numbers. When students work through a problem with dividing fractions, they will go through the steps of “keep, change, and flip.” Once they have changed the division symbol to a multiplication symbol and flipped the second fraction, the students will be ready to use their previous knowledge on multiplying whole numbers. After the numerators and denominators are multiplied respectively and the new fraction is obtained, the students must recall previous knowledge on the reduction of fractions to their simplest form.

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Technology (E1)

A video can be used to engage students and give them a foundation for dividing fractions. The video I chose, which can be found at http://www.youtube.com/watch?v=uMz4Hause-o, is an excellent example of an acceptable engagement tool. In the video Flocabulary uses music and repetition to describe how to perform the task of dividing fractions. This will help the students be able to recall the information about dividing fractions later on when they need to. Flocabulary explains the process step-by-step and then demonstrates the method in action, using two different fractions to help students understand how it works. Then the video goes on to explain why we flip the second fraction in a division problem, which is vital for ensuring that actual learning is taking place and not simple memorization. Students need to know why they perform certain steps and why the trick works. While the cartoon animations are meant to target a younger audience, this clip is easy to follow and the repetitious nature of the music puts an interesting spin on learning mathematics.

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