Grade: Fifth
Essential Question
How do the models and
strategies used with whole
number computation compare
with decimal computation?
How does computing with
decimal numbers change
estimation strategies?
Lesson 8: Multiply Decimals
Standard: NBT.B.7
Add, subtract, multiply, and
divide decimals to hundredths,
using concrete models or
drawings and strategies based on
place value, properties of
operations, and/or the
relationship between addition
and subtraction; relate the
strategy to a written method and
explain the reasoning used.
Vocabulary (Synonyms)
 model
 place value


positions (to
hundredths)
properties of
operations
strategies
Math Practices-
Big Idea
Students will understand
how the operations of
multiplication and division
are related and how those
understandings extend into
decimal numbers to the
hundredths.
 SMP #1 - Make sense of problems and
persevere in solving them.
 SMP #2 - Reason abstractly and
quantitatively.
 SMP #3 - Construct viable arguments
and critique the reasoning of others.
 SMP #4 - Model with mathematics.
 SMP #5 - Use appropriate tools
strategically.
 SMP #6 - Attend to precision.
 SMP #7 - Look for and make use of
structure.
Lesson Tips:
-The standard is broken up in the textbook over 3 lessons (Lessons 7, 8, and 9)
Lesson 7 will cover adding and subtracting decimals to hundredths
Lesson 8 will cover multiplying decimals to the hundredths
Lesson 9 will cover dividing decimals to the hundredths
Lesson 8 Suggested Sequence:
Day 1: Concrete Base Ten Block Manipulation
Week 8
Knowledge Targets




Students must identify models
(e.g., block drawings to represent
tenths and hundredths) and build
them up for addition and
multiplication operations.
Students must properly break
down models (e.g., block
drawings representing tenths or
hundredths, base ten blocks, etc.)
to represent subtraction and
division operations.
Students must recall and use the
properties of addition,
subtraction, multiplication, and
division.
Students must be able to write
down a mathematical
representation of the problem to
solve it correctly based upon the
models being used to solve the
problem. NOTE: The standard
algorithm for utilizing the
operations with decimals to the
hundredths is NOT taught until
6th grade (see 6.NS.2). The
mathematical operations the
students create are based upon the
concrete materials and
translations made during the class
lessons.
Video modeling multiplying decimals using area models and base ten
blocks:
https://www.youtube.com/watch?v=ddhJIZdXRGU
Product Targets

Day 2: Decimal Grid Models
Decimal multiplication area model
http://tidewaterteam.wm.edu/files/2012/05/DOBTB2.pdf
Instructional iReady Teacher Toolbox Resource:

Tools for Instruction Tab-Multiply Decimals
Day 3: Area Model
Use student instruction book pgs. 64, 65, 66, and 68
Day 4: Algorithm
https://www.khanacademy.org/math/pre-algebra/decimals-prealg/multiplying-decimals-pre-alg/v/multiplying-decimals
Instructional Resource (to use to show students area model and base ten
blocks):
https://illuminations.nctm.org/Activity.aspx?id=6377

Students must be able to use
concrete materials to model
strategies for solving addition,
subtraction, multiplication,
and division problems with
decimals to the hundredths.
Students must be able to
create models that explain
strategies for solving addition,
subtraction, multiplication,
and division problems with
decimals to the hundredths.
Students must be able to write
down a mathematical
representation of the problem
and solve it correctly based
upon the models being used to
solve the problem.
Brain Pop:
https://www.brainpop.com/math/numbersandoperations/multiplyingdecima
ls/
Activities
Multiplying Multi Digit
Decimals Worksheet
http://www.cpalms.org/Public/
PreviewResourceAssessment/P
review/55311
Scholastic Order Form
Activity
Games
Card Flip:
-Each student flips 3 cards for and factors.
Students place a decimal between the ones
place and the tenths. First student to find the
product will get the cards. Students with the
most cards at the end wins.
Extra Resources
Teacher-Toolbox on IReady
Website
Math Center Activities:
Represent Decimal Products
Additional Support
Use Scholastic Book Order
Forms. Give students an
amount of money, students will
pick out a book. Ask: What is
the greatest number of that
book you can purchase? How
much change do I owe you?
Instructional Tasks in Math
Instructional Resources
Binder from Summer
Training
Candy Factory
Cider Selling
Ribbon Cutting
Floor Covering
Window Talk
Cooking Measures
Meter Reading 1
Meter Reading 2
Center Activity:
http://www.jennyray.net/upload
s/1/2/9/7/12975776/5thgradede
cimal_fal1.pdf
Sample Test Questions:
4.36 x 1.7=
-Same Game except you flip an factor and a
product, first student to find the missing factor
wins the cards.
Online Games:
Algorithm Practice
http://www.mathplayground.com/howt
o_multiplydecimals.html
https://www.mangahigh.com/enus/math_games/number/decimals/multiply
_decimals
Division
Tim is making granola bars and has 39
cups of granola. If each batch needed 4
cups of granola and he made the greatest
number of batches he could, how much
does he have left over? (Put the remainder
in decimal form.)
Fractions and Decimals
Multiplication/Division
805 backpacks were distributed equally
among 5 schools. How many backpacks
did each school receive?
Place Value
Write this number in words:
691,045.09
Fractions
Mixed Numbers
8/5 – 7/10 =
Robin says that 81.75 = 81 and 4/3. Is she
correct or incorrect? What do you know
about 4/3 that helps you solve this
problem?
Order of Operations
Solving for Unknowns
Writing in Math
13 +(3 ½ - 2 x 6) – 1/4
1/3 + m = 3 and 5/6
Robert’s team jumped rope for ¾ of an
hour. Todd’s team jumped for 0.625 of an
hour. What is the difference in these
amounts of time?
In math, we say that multiplication and
division are inverse operations. Define the
term inverse and explain how you know
this is a true statement.