Lesson Plan #3 – Introduction to Adding and Subtracting Fractions with Unlike
Denominators
Grade: 5th
Day Three: 30 minute lesson
MA Framework Standard: add and subtract fractions with unlike denominators
1. Lesson Objectives
a. Knowledge Outcomes:
The students will be able to add and subtract fractions with unlike denominators
by replacing given fractions with an equivalent sum or difference of fractions with
like denominators (Standard 5.NF).
b. Skill Outcomes:
The students will be able to:
-Find common denominators
-Create equivalent fractions with like denominators
-Add and subtract fraction with like denominators
2. Assessment:
a. Formative assessments
The students will work in pairs to add and subtract a set of given fractions. The
teacher will circulate through the classroom taking mental observations of the
students. Also, towards the end of the class the teacher will ask the students fill out an
exit card answering the question, do you think you could teach adding and subtracting
fraction with unlike denominators to your friends? Why or why not?
b. Summative assessment
In the final cumulative unit test the students will be asked to complete problems in
which they will have to add and subtract fractions with unlike denominators.
3. Materials
Flash cards for exit cards
Flash cards for activities in pairs
4. Sequence of activities
a. Hook:
(Assume there are 24 students in the class) Have half the students stand in one side of
the classroom and the other half on the other side. Write 1/2 on the board. Then write
12/24 on the board. Ask the students to count how many students are in each side.
The answer should be 12 for each side. Write 12/24 = 1/2. Explain that these are
equivalent fractions regardless of the fact that they have different denominators.
b. Activities:
1.The teacher will demonstrate process of adding and subtracting fractions with
unlike denominators
-Find a common denominator ex: 2/3 + 5/4 = /12
-12 is a common denominator of 3 and 4
-Divide the common denominator by the two original denominators
ex: 12/3=4 and 12/4=3
-Multiply the quotient of the division by both numerators
ex: 2x4=8 and 5x3=15
-Form the equivalent fractions ex: 8/12 and 15/12
-Add the numerators of both fractions ex: 8/12 + 15/12 = 23/12
-The teacher will complete a few problems on the board
-The students will take notes as instructed by the teacher
2. Group activity
-The students will divide into pairs
-Each pair of students will get a set of flash cards
-Each flash card will have a different step of the process to complete
-These will be fill in the blank
-Each pair of students will work together to complete the flash cards
c. Differentiation:
Those students who are visual learners will be encouraged to draw fraction bars to
represent each fraction.
d. Wrap-Up:
To wrap up the lesson the teacher will collect the cards from each pair of students.
The students will then be asked to fill out exit cards.
5. Potential Pitfalls
In order to come up with common denominators the students need to be confident with their
multiplication tables, if they are not this lesson will not be successful.
6. Reflections
The differentiation portion of this lesson needs to be strengthened. Although, ideally the
lesson would take 30 minutes, it is very likely that it will take longer. It all depends on the
clarity in which the teacher explains the material and the students’ ability to work effectively
in pairs.