Lesson 21 Multiply More Decimals

- Let’s multiply decimals.

Warm-up Estimation Exploration: Central Park

Central Park is a large park in Manhattan. It is about 3.85 kilometers long and 0.79 km wide. What is the area of Central Park?

Record an estimate that is:

Image of map of Central Park.

too low	about right	too high

Activity 1 Multiply More Decimals

Problem 1

Explain or show why each pair of expressions is equivalent.

$7.2 \times 5.3$ and $(72 \times 53) \times 0.01$
$6.5 \times 2.8$ and $(65 \times 28) \div 100$
$31 \times 0.44$ and $(31 \times 44) \times \frac{1}{100}$

Problem 2

Find the value of the products in the previous problem.

Activity 2 Choose Your Strategy

Find the value of each product.

$7.3 \times 4.2$
$38 \times 0.55$
$285 \times 0.17$

Practice Problem

Problem 1

Explain or show why $5.6 \times 3.4 = (56 \times 34) \times 0.01$ .
Use this strategy to calculate $5.6 \times 3.4$ .