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: /multiply-a-decimal-by-a-one-digit-whole-number, multi-digit-whole-numberhttp:// 5/multiply-a-decimal-by-a-one-digit-whole-numberhttp:// multi-digit-whole-number Copyright © 2013 Innovative Educational Programs. Reproduction rights granted to CHILD Teachers and permitted only for use as instructional material.

Copyright © 2013 Innovative Educational Programs. Reproduction rights granted to CHILD Teachers and permitted only for use as instructional material.

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.

Problem: Ben, Barry and Brian each have 27 cents. How much do they have altogether? Copyright © 2013 Innovative Educational Programs. Area Model - Decimal x Whole Number 0.27 x 3 = x 3 = 0.81

Multiplying - Decimal x Whole Number Problem: Brendon was selling a car for $1,000. He had to charge sales tax of How much tax did he charge? The equation: 1,000 x 0.65 = Sales Tax Step 1: Multiply 0.65 x 100 (or 10 2 ) = 65 Step 2: Multiply 1,000 x 65 = 65,000 Step 3: Divide 65,000 by 100 = 65,000 ÷ 100 (or 10 2 ) = 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 Copyright © 2013 Innovative Educational Programs Problem: What is the product of 0.8 x 0.6? 0.8 is represented by 8 columns of ten – colored in red. 0.6 is represented by 6 rows of ten – colored in blue decimal place X decimal place decimal places 0.48 is represented by purple: a combination of both red and blue.

Multiply - Decimal x Decimal What is the product of 1.3 x 1.8 = ? Copyright © 2013 Innovative Educational Programs. 1 x 1 =1 1 x 0.8 = x 0.3 = x 0.3= Find the partial products. 1.0 x1.0 = x 0.3 = x 0.8 = x 0.8 = 0.24 Then add the partial product. 1.0 x1.0 = x 0.3 = x 0.8 = x 0.8 = The product of 1.3 x 1.8 = 2.34

1.02 x x x x x x x x x 10

5 x x 3.54 x x 83.6 x x x x x

36.5 x x x x x x

NumberAnswer , NumberAnswer Answer Key for Copyright © 2013 Innovative Educational Programs.

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