Prior Knowledge: Students should be able to add and subtract fractions with like denominators. Students should be able to change improper fractions to mixed numbers. Students should have be able to estimate fractions and state whether they are more or less than a half or more or less than a whole.
Lesson Objective: By the end of this lesson you will have a better understanding of how to add fractions with unlike denominators.
Materials: Get out paper and a pencil as well as your fraction strips!
Ready to Add!
For the following lesson I am going to direct you to a video that will introduce you to adding fractions with unlike denominators. The lesson will give you helpful tips and strategies for adding fractions in a real world scenario. Get ready to use your fraction number sense! After the video I will give you some more problems to try solving.
http://www.youtube.com/watch?v=UnMOM-_kMbQ&feature=relmfu
What a great lesson huh?!? I would recommend trying the 30-day trial! If not, we can use the same strategies that you learned during the lesson using your fraction strips.
Let's Practice!
To practice what you just learned, I want you to follow the steps below with each set of fractions.
Sets of Fractions:
A. 1/2 + 3/4
B. 4/5 + 1/10
C. 1/3 + 5/6
D. 3/8 + 1/2
E. 5/6 + 1/12
F. 8/10 + 1/2
1. Write a word problem to go along with your two fractions. Think about hte problem that the lesson used.
2. Ready to solve?!? Estimate first! Remember the estimation lesson we did and be sure to ask your self, is the fraction more than half or less than half. Is the fraction more than a whole or less than a whole? Once you ask yourself those questions for each fraction, go ahead and find a reasonable estimate for your problem.
3. Use your fraction strips to solve the problem like she did in the lesson OR find a common denominator! Watch the video again if you need to review what she did. Make sure you make your improper fractions proper!
4. Once you have your answer, compare it to your estimate, were you close?
5. Finally, write a complete sentence stating your answer! For example, T'mya and Sarah have 1 and 1/2 pizzas.
6. Post your word problems and answers on the blog so I can check them out!
Thinking Behind the Lesson:
Adding fractions with unlike denominators can be a tough concept to teach and a tough concept to learn. Before exploring this concept, students should be well on their way to developing a solid fractional number sense. In the past, I have jumped into adding and subtracting fractions too soon, before my students really understand what a fraction is and how it compares to a whole. This has been a mistake on my part and has been detrimental to my students' abililty to understand this concept. Yes, we can teach our students the algorithm for adding fractions with unlike denominators, but it is much more important for our students to truly understand what is happening.
In John A. Van de Walle's book, Elementary and Middle School Mathematics: Teaching Developmentally , he states that students should use a variety of models and strategies when teaching fraction computation. He discusses the importance of allowing students to explore different ways of solving the problems and to defend their solutions as these ideas will help children build a foundation and familiarity with fractions (Van de Walle p. 265). This short video exposes students to two different ways of solving an addition problem with unlike denominators. It also stresses the importance of estimation and fractional number sense.
Reflection:
*This can be a helpful introduction or reinforcement for introducing your student to adding fractions with unlike denominators. However, as Van de Walle states in his book (see above), it is important to expose our students to many different strategies and models when teaching fraction computation. Students will also need a lot of time to explore this concept in order to truly develop an understanding.
*Another great model or strategy for teaching this concept is by using Cuisinaire Rods. Check out this video:
http://www.youtube.com/watch?v=0BSvSGIWvMs&feature=relmfu
*In the practice part of this lesson, I have given fraction sets where students will only need to change 1 denominator. Once your student becomes familiar with the concept, challenge them by giving them two fractions where you would need to come up with a DIFFERENT common denominator. For example, 1/2 + 2/3.
*Continue to reinforce this concept through real world application. Cooking is a great place to do this!
References:
Van de Walle, J.A. (2004). Elementary and middle school mathematics: Teaching developmentally. Boston: Pearson.
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