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Lesson 6: Adding and Subtracting Fractions with Unlike Denominators
Grade Level: 6
Unit: Fractions
Date: Wednesday, 11/9/11
Time: 40 minutes (short day)
15 minutes from Language Arts
Objectives
SWBAT create a graphic organizer (in the form of a 12 page Burrito Book (BB)) that contains strategies that will help them solve arithmetic problems that involve fractions.
SWBAT compare and order fractions.
SWBAT add & subtract fractions with unlike denominators.
SWBAT reduce fractions to their simplest form.
Prior Knowledge
Students must be able to add and subtract whole number.
Students must have a general understanding of factors.
Students must be able to divide whole numbers.
Students should be able to multiply whole numbers.
Students should have practice reducing fractions and finding the GCF.
Materials/Resources
Students: assembled BB, 2 small sticky notes, Adding and Subtracting Homework 2, Holt Book, pencils, math journals
Teacher: whiteboard, dry erase markers, eraser, copy of Holt, graded students work (lesson 4 homework: Comparing and Ordering Fractions)
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Time
3 min
2 min
10 min
10 min
15 min
5 min
15 min |
Lesson
New Routine Write on board: 1. Turn in homework 2. Get out Burrito Books 3. Open Planners
Pass back graded work
Pass out tonight's homework -students write problem numbers on homework then put away (Choose 5 from each side of the Adding and Subtracting Homework, Retry Comparing and Ordering Fractions: Do odds)
Go over objectives
Have students get out a sheet of paper and make a prediction for the following problems: compare: 4/9 and 5/7 order: 3/8, 2/10, 4/5 We will return to this so keep your paper handy.
Least Common Denominator (LCD) The smallest multiple 2 or more denominators have in common. I do: 1/3 and 4/6 3: 3, 6, 9, 12, 15, 18, 21, 24 6: 6, 12, 18, 24, 30 6 is the LCD
You do: 2/7 and 1/4 7: 7, 14, 21, 28, 35, 42 4: 4, 8, 12, 16, 20, 24, 28 28 is the LCD
Comparing and Ordering Fractions Review After looking over everyone's homework from Monday night, I decided we need to review comparing and ordering fractions. What do you remember about comparing and ordering fractions? (We know that when 2 fractions have the same denominator, the fraction with the larger numerator is bigger. When 2 fractions have the same numerator, the fraction with the larger denominator is smaller.)
How can finding the LCD help us solve the problems you made a prediction about earlier? (If we find the LCD and change the fractions so they have the same denominators, the fraction with the larger numerator is bigger.)
Please take 3 minutes to solve the problems you made a prediction about at the beginning of class.
Rewrite problems on board. Popsicle stick volunteers come to board to solve. Students narrate their steps. Narrate for them if they cannot or are not comfortable doing so.
+ and – unlike fractions 1. Find LCD. 2. For each fraction: what do I need to multiply the denom by to get the denom to the LCD? 3. Multiply num and denom by that number. 4. Repeat steps 2-3 for fraction 2. NOW THESE ARE LIKE FRACTIONS! We know the rest from yesterday's lesson: 5. Add/subtract numerators. 6. Reduce
I do: 1/3 and 4/6 we found LCD was 6 (mult. 1 and 3 by 2. Nothing for 4/6)
You do: 2/7 and 1/4 we found LCD was 28 (mult 2 and 7 by 4). (mult 1 and 4 by 7).
BREAK
Language Arts: Mrs. ____ was kind enough to let us borrow some time from language arts to retry Monday night's homework. If you recall, you did the odds. Please retry the evens. When you finish your first problem raise your hand so that Mrs. ____ or I may check that you are on the right track.
Do not move on until Mrs. ____ or I have given you the okay. You will have 15 minutes to work on your retrys. If you finish, turn it in and start on your adding/subtracting homework. |
Monitoring Assessment
Students write in BB
Can you define LCD? Take a guess!
Popsicle stick volunteers
Remind students to look in burrito books. Call on 1-3 students.
Call on 1-3 students, guide if necessary.
Walk around and observe
Popsicle Stick Volunteers
How do we add and subtract LIKE fractions? Call on 1-3 students. Remind them to look in Burrito Books.
Popsicle Stick Volunteer
With the help of my mentor teacher, all student work is checked. |
Adaptations/Modifications
ESOL: I write all notes that should be in student Burrito Book's on the board. This will help the student keep up. I check with the class before erasing anything from the whiteboard.
TAG: When finished be an “expert” and answer questions of classmates?
Special Needs All students check with teacher after finishing first problem.
Literacy NA
Other
Reflection
What's next?
Multiplying fractions
What worked?
I was so glad that I corrected student work in a timely manner. It would have been awful to wait to correct the week's work until the weekend and not be able to review Monday's lesson until the following week. Monday's lesson was still fresh enough that the review was successful.
I am lucky to have the same group of students 2 periods in a row. I was relieved to be able to use part of Language Arts to guide students through their homework retrys. I think this really reinforced students' understanding of the concept. It was also nice to have my mentor teacher's assistance in the review process because I was able to reach more students.
What would I change?
It took me an entire evening to grade 2 days of classwork and homework (for 2 classes). It was a miserable experience. In the future, I will have students correct their work in class. I think this method of grading is especially effective in math. This will be an instant review for students, give them extra practice, and will eliminate a large amount of my paperwork. However, I don't think I can use this method of correcting papers at this time. I have too much content to get through in my remaining lessons.
I worry I traded the reinforcement of one concept for the comprehension of another. While I am glad I reviewed Monday's lesson, I wish I had had more time for students to practice adding and subtracting unlike fractions. I will have to make sure I spend extra time reviewing adding and subtracting unlike fractions next week.
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