Recalling Prior Knowledge of Adding and Subtracting Fractions

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Students will be able to add and subtract fractions by using common denominators and equivalent fractions.

Big Idea

The denominator represents the WHOLE and the numerator represents the BITS/PIECES so in order to add fractions we need to have the same denominator.

Language Objective and Prior Knowledge

Language Objective: Students will talk about adding or subtracting using academic language: numerator, denominator, and equivalent. Students will be able to rewrite fractions to have common denominators

Prior Knowledge: in 4th grade students started working on adding and subtracting fractions with like denominators. Some will have knowledge of common denominators. 

Math Blast - Lesson Activator

15 minutes

Math Blast Number of the Day 29

Math Blast is a quick, fun, fast-paced math game! It doesn't require a lot of materials - just the PowerPoint, music, white boards, and dry erase markers. I begin every day with a Number of the Day.

Math Blast is also a great place to work on Common Core skills, especially critical thinking skills, discourse and collaboration!

I usually play music while students are working (it is the "Blast" in Math Blast). They have to the end of the song to fill in their board.

In the beginning this is more time than most need, but they will use all of the time when the numbers get bigger. Math Blast is a great way to pre-teach a concept and is really good scaffolding, especially for those struggling learners. I like to add new concepts that will be learning in the near future into Math Blast. This way students are familiar with new concepts when I go to teach them. If they haven't figured out the work through Math Blast they will have at least seen the concept. 

I allow table mates to support each other, this is also a good way to support struggling learners.

The basic content my Math Blast covers is:

  • Begin with prior knowledge tasks, factoring GCF, LCM. In 5th grade this is really good to have understanding for going into fractions.
  • I always add some rounding and estimation, good tools to know and it is pre-teaching our next lesson.
  • I always like to end with a word problem to challenge and support students' skills in answering a problem with what the question is requesting them to do.


The closing piece of Math Blast is See, Think, and Wondering.

See, Think, Wondering

5 minutes

I end Math Blast and lead into my lesson with a See, Think, Wondering. The art I choose always relates to the unit I am teaching. We extend our thinking today, by looking at how Mondrian's work inspired Yves St. Laurent clothing design.

See, Think, Wonder is a dynamic way to get your students to think deeper about a subject without them knowing that they are doing it.

The SEE part is pretty basic thinking. I see….

The THINK part is intended to get students to think about things in ways they haven't before. This is a fun way for students to make connection to the things we're learning in math. In my class, we'll be thinking about math and art.  I use art because I am passionate about art. Use examples of things that ignite your passion! This art makes me think about….

And the WONDER requires enough engagement with the topic (the art) to be able to come up with a question. This art makes me wonder if….

See, Think, Wonder is my way to getting their brains ready to think about math and I find that the transition is great. It is also a quick chance to expose my students to different types of art.

Note: I've added a See, Think, Wondering separate from the Math Blast in case you want to do it by itself. It is also attached at the end of the Math Blast PowerPoint.

Note: You don’t have to use art; I use art because I am passionate about art. Use examples of things that ignite your passion!

The Elevator Speech

10 minutes

Concept: This lesson specifically addresses Common Core Standard 5.NF.A.1: Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators.

It is always amazing how much students forget over the summer. The most important thing students need to recall is that you need to have like denominators in order to add or subtract fractions (they need to have the same size pieces) If the denominators are unlike you need to find equivalent fractions so you can add or subtract (4.NF.1 & 4.NF.2)

Script, if needed: I start out talking about food, fractions are GREAT for food. And what is better to talk about then PIZZA! (I might pre-draw some pizzas with the same piece sizes and some with different piece sizes. For example: some pieces that have 1/4s, 1/5s, 1/3s and 1/6s. It is easy to see when the slice size is the same size you can add and subtract, but what to do when they are not!)

Work It Out

40 minutes

Challenge the class, even if they know how to add and subtract with unlike denominators, to make a model that shows how to be able to add/subtract the following factions. Note: if you have transparencies they work great for this exercise. When comparing fraction strips, if you draw these out (have students do this) on transparencies you can over lap them and see why a fraction strip model is successful or not!

½ + ½

½ + ¾

¾ - ¼

½ - ¼

¾ - 2/5

*For those who finish, have them create their own to challenge the class, problem and answer key!

This lesson is to check for understanding and to see what knowledge they do recall. Also, while round fraction 'pizzas' are a good model, suggest that they use fraction strips.

The fractions I use as examples (above) are chosen because they are benchmark fractions and easy to manipulate. They are also easy to model. This choice gives all students an opportunity to be successful.

The last fraction subtraction problem is an exception, It was chosen because it is going to be hard to model. I always like to challenge students.

Closing The Deal

10 minutes

The Closing It section of the lesson is very important. This opportunity allows you to bring the class back together and have them make the connection to the learning objective of the day. You should also make sure that you make a connection to the word of the day. This closing gives students the opportunity to make the connection to the launch and they work that they did. It is also another chance to give a quick formative assessment to check for understanding.

Talk about the struggles, check in for understanding, talk about stacking. This is a good place to bring misconceptions to class. I like to have the students lead this discussion as it allows me the opportunity to hear and listen to the students. An easy way to do this is to ask a blanket question of 'who was struggling with fractions' or 'did anyone struggle and want to share their success?' or 'can anyone give us an example of where you struggled so the class can help us work it out'

I also like to have students that were successful to share their thinking. These students I usually talk with during the work time and ask them if they are willing to share.

You can also write a new problem on the board and do a 'turn and talk' with partners (I always have students sitting with their table mates on the floor) and discuss how to solve the problems. Then I randomly call on students and ask them to explain what their partner told them, this holds students accountable for listening!

Quick Assessment

5 minutes

The Post-It Poster: ½ + ¾ = _______ (The answer must be "explained" with a model.)

The Quick Assessment is supposed to be quick and on the easy to medium difficulty level. You are checking to see if students understand the basic concept of the lesson. If you make the problem difficult you are adding a different level of assessment. If you are teaching a higher level class adding a difficult layer might be appropriate but please note that I do not find it necessary to add this level.

Look-Fors: Misconception that 1/2 + 3/4 = 4/6, still adding denominators and not finding equivalent fractions. I am also looking to see if students are using models correctly to show their thinking (see the Reflection: Models that Work in the Work It Out section).