Decimal Detective
Multiplying Decimals
Intermediate Math
CCSS: 5.NBT.1, 5.NBT.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.
Additional Information for teacher about activity: This activity encompasses; using mental math to multiply by
10, 100, 1000, estimating products of whole numbers and decimals, products of whole numbers and decimals,
and product of two decimals. The teacher can select all or part of the cards for differentiation. Additional blank
cards are included for teacher use.
What’s included:
□ Task Card in WORD
□ Anchor Charts
□ Student Activity Cards for self or partner directed work
□ Answer Key for self-checking
□ Materials Needed: number cube, markers, CHILD Activity Game Board and Challenge Question Answer Sheets
□ Technology Connection: http://www.ixl.com/math/grade-5/estimate-products-of-decimals,
http://www.ixl.com/math/grade-5/multiply-a-decimal-by-a-power-of-ten, http://www.ixl.com/math/grade5/multiply-a-decimal-by-a-one-digit-whole-number, http://www.ixl.com/math/grade-5/multiply-a-decimal-by-amulti-digit-whole-number
Copyright © 2013 Innovative Educational Programs.
Reproduction rights granted to CHILD Teachers and permitted only for use as instructional material. www.ieponline.com
____________S tation
Activity Name: Decimal Detective
Standard: Number and Operations in Base Ten
Skill/Objective: (COPY IN YOUR PASSPORT) Multiplying Decimals
Directions:
1. Work in a group of 2-3 partners.
2. You will need a set of cards, markers for each student, a number
cube, an answer card and a CHILD activity game board.
3. Shuffle cards and place face down.
4. Tallest partner goes first.
5. Pick a card, read it aloud and answer. Use the Anchor Charts to
help you solve the problems.
6. Partner to the left checks the answer.
7. If correct, roll the number cube and move that many spaces on
the board. If not correct, place the card at the bottom of the pile.
8. Take turns until someone reaches the end of the board.
Challenge: Write your answer on a Challenge Question Answer Sheet.
Two years ago, a computer company had sales that totaled 6.5 million
dollars. Last year the sales increased 2.5 times over the previous year.
What were the sales totals last year?
Reflection: I think the easiest strategy or model to use to multiply
decimals is . . .
WHEN COMPLETED
□ check
□ place in folder
□ hand in
□ other _________________
Intermediate Math
Copyright © 2013 Innovative Educational Programs. Reproduction rights granted to CHILD Teachers and permitted only for use as
instructional material. www.ieponline.com
STATION TASK CARD
Estimating - Decimal x Whole Number
• Problem: Ben, Barry and Brian each have 27
cents. How much do they have altogether?
• The equation: 0.27 x 3 = ?
• To solve: use estimation
 0.27 x 3 =
 0.30 x
3 = 0.90 or approximately 90 cents.
Copyright © 2013 Innovative Educational Programs.
Area Model - Decimal x Whole Number
Problem: Ben, Barry and Brian each have 27
cents. How much do they have altogether?
0.27 x 3 = 0.27 + 0.27 + 0.27
0.27 x 3 = 0.81
Copyright © 2013 Innovative Educational Programs.
Multiplying - Decimal x Whole Number
• Problem: Brendon was selling a car for $1,000. He
had to charge sales tax of 0.65. How much tax did
he charge?
The equation: 1,000 x 0.65 = Sales Tax
Step 1: Multiply 0.65 x 100 (or 102) = 65
Step 2: Multiply 1,000 x 65 = 65,000
Step 3: Divide 65,000 by 100 = 65,000 ÷ 100 (or 102) = 650
The tax charge is $650.
• When you multiply a decimal to get a whole number 0.65 x 100,
the answer must be divided by 100 to find the actual answer.
Copyright © 2013 Innovative Educational Programs.
Area Model: Multiply - Decimal X Decimal
Problem: What is the product of 0.8 x 0.6?
0.8
0.8 is represented by 8 columns
of ten – colored in red.
0.6 is represented by 6 rows of
ten – colored in blue.
0.6
0.8
X 0.6
0.48
1 decimal place
1 decimal place
2 decimal places
0.48 is represented by purple: a
combination of both red and
blue.
Copyright © 2013 Innovative Educational Programs.
Multiply - Decimal x Decimal
• What is the product of 1.3 x 1.8 = ?
1.0
0.3
Find the partial products.
1 x 1 =1
1.0
1.0 x1.0 = 1.0
1.0 x 0.3 = 0.3
1.0 x 0.8 = 0.8
0.3 x 0.8 = 0.24
1 x 0.3
=
0.3
Then add the partial product.
0.8
1 x 0.8 = 0.8
0.8 x
0.3=
0.24
1.0 x1.0 = 1.0
1.0 x 0.3 = 0.3
1.0 x 0.8 = 0.8
0.3 x 0.8 = 0.24
2.34
The product of 1.3 x 1.8 = 2.34
Copyright © 2013 Innovative Educational Programs.
0.8325 x 1000
4.56 x 10
1
3.625 x 100
2
7
3
1.02 x 100
28.6 x 10
4
82.593 x 1000
50.375 x 10
5
9.83 x 100
6
4.26 x 10
8
9
5 x 8.2
20.6 x 3.5
10
0.9 x 8
4 x 0.14
11
8.7 x 5.3
3.6 x 2.1
13
5.25 x 0.4
14
0.6 x 36
16
12
15
62.5 x 0.13
17
18
36.5 x 0.7
243 x 1.5
19
212 x 0.4
70.6 x 0.8
20
21
3.36 x 1.4
8.21 x 1.7
22
23
24
25
26
27
Answer Key for
Number
Answer
Number
Answer
1
45.6
13
7.2
2
832.5
14
7.56
3
503.75
15
46.11
4
362.5
16
2.1
5
286
17
21.6
6
102
18
8.125
7
82,593
19
25.55
8
983
20
364.5
9
42.6
21
56.48
10
41
22
84.8
11
72.1
23
13.957
12
0.56
24
4.704
Copyright © 2013 Innovative Educational Programs.
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