How do you multiply

0.5 x 0.3?

In this lesson you will learn how to multiply decimals by decimals by using an area

model.

Let’s ReviewLet’s Review

Hundreds

Tens Ones

2 groups of ten = 20

3 single units = 3

1 group of 100 = 100

Ones

Hundreds Tens Ones

1 2 3

Let’s ReviewLet’s Review

Whole Unit (Ones)

Tenths

Hundredths

Let’s ReviewLet’s Review

2 Tenths 3 Hundredths

Ones Tenths

Hundredths

1 2 3

1.23

1 Whole

Let’s ReviewA Common Mistake

Forgetting to take the decimal into consideration when multiplying.

0.3 x 0.5 ≠ 15

Let’s ReviewCore Lesson Smart Estimate0.5 x 0.3

0.5 is

of is

Smart estimate: A little more than 0.1

≈ 0.1

is close to

0.3 x 0.5

≈ 0.2 = x 0.5

Let’s ReviewCore Lesson

Ones Tenths

Hundredths

0 1 5

This is a reasonable

answer since it is close to my

smart estimate

0.5 x 0.3

=

Let’s ReviewCore Lesson

Susanna has 0.4 of a box of paper, but she promised to share 0.5 of it with her friend. How

much paper will she have?

0.5 is

of is Smart estimate is 0.20.4

x 0.5

Let’s ReviewCore Lesson

Ones Tenths

Hundredths

0 2 0

This is a reasonable

answer since it matches my

smart estimate

0.4 x 0.5

=

In this lesson you have learned how to multiply decimals by decimals by using an area

model.

Let’s ReviewGuided Practice 0.6 x 0.4

Let’s ReviewExtension Activities

0.5 x 0.7 is 0.35. Explain why the product of these two decimals is smaller thank he two multipliers. Use an area model to help you explain.

Let’s ReviewExtension Activities

What is 0.3 x 0.4? How would the answer be different if the problem was 0.3 x 0.04?

Let’s ReviewQuick Quiz

Which area model shows 0.4 x 0.7?

A B C