Download Subtracting Mixed Numbers Lesson

Fraction Subtraction Lesson Plan
I. Purpose:

Students will be introduced to a concrete method of subtracting fractions while
using regrouping.
Computation and Estimation
Focus: Multistep Applications and Order of Operations
5.6
The student will solve single-step and multistep practical problems involving addition and
subtraction with fractions and mixed numbers and express answers in simplest form.
II. Objectives:

Given a subtraction problem using mixed numbers, students will be able to
regroup and find the difference between those numbers using concrete methods
and manipulatives with up to 95% accuracy.
III. Procedure: Includes three components
a. Introduction

Have students sit on the red carpet.

Students will be told that they will be investigating a new way to look at
subtracting mixed numbers and fractions using pictures and manipulatives
(counters).

Review the rules of division (Can’t divide by 0, anything divided by itself is 1, 0
divided by anything is 0) by showing how division is how many times a number
can add into something.

Review the connection of fractions to decimals. (Fractions are conversions of
decimals)
Revised: September 2012

Review in one problem the regrouping method introduced by Mrs. Smith
b. Development
 Write the mixed number 3 1/4th on the board. Then, draw boxes next to the number
on the board to represent wholes. For the 1/4th of a whole, make part of a box but
not the full box.
a. Inform students that the reason why you only draw a part of a box is
because you know that because the 1/4th is a fraction, it’s only part of a
whole.
b. After this explained, tell the students you also want to represent the wholes
in their fraction forms. Do this by writing their fractions (4/4) into each
box. Tell the students you do this as too many numbers can often make the
problem more confusing.
 Then, write 2 5/8th on the board. Ask the students how many boxes and partial
boxes you will need for this number.
 Now, inform the students you will be subtracting 2 5/8th from 3 1/4th. Ask the
students what they know from previous lessons they need to do to subtract two
fractions.
a. For this, the students should know the fractions should have like
denominators.
 Demonstrate to the students the idea of eliminating; because the whole numbers
need to be removed, you can cross 2 boxes out from the 3.
 Then, ask the students if 5/8th can be taken away from 2/8th. Ask the students if
they know what they have to do to make this possible
Revised: September 2012
a. Students should know to regroup the last remaining whole with the floating
fraction to make 10/8th.
 Lastly, complete the subtraction and find the remainder.
 Do this again for 6 2/3 – 3 11/12. Call upon students to do each step and reiterate
what should be done.
 Using an Elmo device, introduce the worksheet they will be working on and the
manipulatives they will be using (The counters).
 Instruct the student they need to solve the subtraction problems with their groups
using the method they just learned, but they may also use manipulatives to help
them solve the problems.
 On a blank paper, demonstrate subtracting 2 5/6 from 5 2/3.
a. Using the counters, create 5 2/3 by making three groups out of three
counters each, with the last group being made of 2/3.
b. When converting the denominators, show the students that they can either
add to their wholes to make it a represent the fraction.

This may be confusing visually for some students, so showing
another method of stacking the counters on top of each other
c. Finish the problem then by asking how much they need to eliminate in the
wholes, then how they can solve the remaining 5/6 being taken away from
2/3.
 Have the students return to their seats and have group leaders grab the worksheets
for their groups.
 Observe the groups and assist when necessary.
Revised: September 2012
a. Mrs. Scott and Mr. Paris will be working on assisting the high need
students.
b. Mrs. Smith can help assist in other groups.
c. Summary

After about 15 minutes, have the students stop.

Review the major keywords “regrouping” and “elimination” by demonstrating
what each is on the board.
I. “regrouping” – turning a whole number into a fraction and adding it to
the already existing old fraction.
II. “elimination” – having holes cancel each other out.

Further review using this method in stations and in later work.
IV. Materials needed for the lesson
a. Counters in bags for 7 tables, Whiteboard, Markers, Pencils, “Mixed Fractions
Addition and Subtraction with Unlike Denominators” worksheet
V. Evaluation Part A:

Students comprehension of subtracting mixed numbers will be assessed by their
accuracy on their answers to their worksheet;
o Their knowledge of making like denominators
o Their responses to reviewing the terms at the end of the lesson.
o Their use of manipulatives
o Their use of the concrete method on their worksheets
o The accuracy of their answers to the worksheet questions
Revised: September 2012
VI. Evaluation Part B:
 Did the students meet your objectives?

How do you know?

Did your lesson accommodate/address the needs of all your learners?

What were the strengths of the lesson?

What were the weaknesses?

How would you change the lesson if you could teach it again?
Revised: September 2012