Number and Operations in Base Ten
4
Objective
Multiply With a
One-Digit Multiplier
Students build on and practice with the multiplication concept of repeated
addition by using Base Ten Blocks to multiply a one-digit number by a
two-digit number. This practice is important for students to build fluency
in multiplication. This lesson provides students with a foundation for later
lessons on multiplying by 5, by 10, and by larger numbers.
Common Core
State Standards
■■ 4.NBT.5 Talk About It
Discuss the Try It! activity.
■■ Say: You arranged 3 groups of 21. Write a number sentence to show this
problem. Ask: How else could you have modeled 3 × 21 using blocks?
■■ Ask: What was the total number represented by your blocks? Say: Write a
number sentence to show this multiplication problem with its answer.
■■ Ask: How would you use the blocks to solve the problem 2 × 28? Students
should note that they will regroup the 16 units into 1 rod and 6 units.
Explain how this regrouping is like “carrying” a number from the ones
place to the tens place when multiplying on paper.
Solve It
With students, reread the problem. Have students draw a picture to show
the number of leaves Ms. Parson’s class will collect during the entire month.
Ask students to write a number sentence to show the multiplication problem,
including the answer, and explain in writing how they solved the problem.
More Ideas
For other ways to teach about multiplying with a one-digit multiplier—
■■ Write several multiplication problems on the board for students to solve.
Provide one-digit by one-digit problems, then have students move on to
one-digit by two-digit problems. Have pairs of students use Color Tiles
to model and solve the problems.
■■ Write 3 × 16, 2 × 32, and 4 × 19 on the board. Ask small groups of students
to use Cuisenaire® Rods to model and solve each problem.
Formative Assessment
Have students try the following problem.
Each of Mr. Carrido’s 23 students brought 2 snacks to take on their field trip.
How many snacks did the students have altogether?
50
A. 25
B. 46
C. 54
D. 68
Try It!
20 minutes | Groups of 4
Here is a problem about multiplying with a one-digit multiplier.
Materials
Introduce the problem. Then have students do
the activity to solve the problem. Distribute Base
Ten Blocks and a Place-Value Chart (BLM 5) to
groups of students.
1. Have students model 21 with the blocks.
Instruct students to represent this number on
their Place-Value Chart.
3. Have students find the total number
represented by all the blocks. Say: Count all of
your blocks. Ask: What number do you have?
• Base Ten Blocks (30 units and 15 rods
per group)
• Place-Value Chart (BLM 5; 1 per group)
• pencils (1 per group)
Number and Operations in Base Ten
Ms. Parson’s class collects 3 different types of leaves every day to study
during science. Brian calculates that there will be 21 days of class this
month. How can Brian find the total number of leaves the class will collect
this month?
2. Say: We want to make 3 groups of 21.
Arrange two more groups of 21 with blocks,
then draw them on your Place-Value Charts.
Watch for students who don’t grasp the concept
of multiplication as repeated addition. Write 2
× 12 on the board. Say: You need to find the
number 12 “two times.” So multiplying 12 by 2
is the same as adding 2 groups of 12 together.
Have students model 2 × 12 with blocks and
then on their Place-Value Charts. Point out to
students that they have made a group of 12 two
times. Then have students add to find the total.
51
Lesson
4
Name Number and Operations in Base Ten
Answer Key
Use Base Ten Blocks to build each expression. Write
the multiplication expression and product. (Check students’ work.)
1.
3. 2.
32
2
64
22
4
88
13
3
39
_____
× _____
=_____
_____
× _____
=_____
_____
× _____
=_____
Build each problem using Base Ten Blocks. Sketch the model in a
Place-Value Chart. Regroup as needed. Write the product. (Check students’ models.)
735
4
. 245 × 3 = _______________
Thousands
Hundreds
Tens
Ones
Tens
Ones
4,248
5
. 2,124 × 2 = _______________
Thousands
Hundreds
52
190
6. 38 × 5 = ________
64
7. 16 × 4 = ________
663
8. 221 × 3 = _______
3,120
9. 1,560 × 2 = _____
792
1
0. 132 × 6 = _______
468
1
1. 117 × 4 = _______
Hands-On Standards, Common Core Edition
Download student pages at hand2mind.com/hosstudent.
© ETA hand2mind™
Find each product.
Name Key
Answer
Challenge! How many of each Base Ten Block do you have
before regrouping when you multiply 46 × 3? Explain how to
regroup to write the product. Draw a picture to help.
Challenge: (Sample) 12 rods and 18 units; 18 units regroups to 1 rod and 8 units.
One rod added to the 12 rods make 13 rods. Thirteen rods regroups to 1 flat and
3 rods. The model of the product has 1 flat, 3 rods, and 8 units. The product is 138.
© ETA hand2mind™
Download student pages at hand2mind.com/hosstudent.
Hands-On Standards, Common Core Edition
53
Lesson
4
Number and Operations in Base Ten
Name Use Base Ten Blocks to build each expression. Write
the multiplication expression and product.
1.
3. 2.
_____ × _____ =_____ _____ × _____ =_____ _____ × _____ =_____
Build each problem using Base Ten Blocks. Sketch the model in a
Place-Value Chart. Regroup as needed. Write the product.
4
. 245 × 3 = _______________
Thousands
Hundreds
Tens
Ones
Tens
Ones
5
. 2,124 × 2 = _______________
Thousands
Hundreds
52
6. 38 × 5 = ________
7. 16 × 4 = ________
8. 221 × 3 = _______
9. 1,560 × 2 = _____
1
0. 132 × 6 = _______
1
1. 117 × 4 = _______
Hands-On Standards, Common Core Edition
www.hand2mind.com
© ETA hand2mind™
Find each product.
Name Challenge! How many of each Base Ten Block do you have
before regrouping when you multiply 46 × 3? Explain how to
regroup to write the product. Draw a picture to help.
© ETA hand2mind™
www.hand2mind.com
Hands-On Standards, Common Core Edition
53
Hundreds
Tens
152 152
Ones
5
BLM 5 Place-Value Chart
© ETA hand2mind™
Thousands
Place-Value Chart
BL M
Name