Lesson 17 Multiply Decimals and Whole Numbers

- Let’s multiply whole numbers by tenths and hundredths.

Warm-up True or False: Place Value Products

Decide if each statement is true or false. Be prepared to explain your reasoning.

$100 \times 0.01 = 1$
$10 \times 0.1 = 0.01$
$10 \times 0.01 = 0.1$

Activity 1 Multiply Decimals By Whole Numbers

Problem 1

Problem 2

Find the value of each expression in a way that makes sense to you. Explain or show your reasoning. Use the grids, if needed.

$2 \times 0.7$
$2 \times 0.08$
$2 \times 0.78$

Activity 2 Using Whole Number Products

Problem 1

Find the value of each expression. Explain or show your reasoning.

$3 \times 0.5$
$5 \times 0.3$
$7 \times 0.02$

Problem 2

Kiran wrote this explanation to describe the strategy he used to multiply a whole number by some tenths:
“I just turn the numbers into whole numbers, multiply them, and call them tenths.” (Pause for teacher directions.)
Can you use Kiran’s reasoning to find the value of $6 \times 0.07 ?$ Explain your reasoning.

Practice Problem

Problem 1

Shade $5 \times 0.07$ on the diagram.
What is the value of $5 \times 0.07$ ? Explain or show your reasoning.
What is the value of $5 \times 0.2$ ? Use the diagram if it is helpful.