How do you multiply

7 x 0.15?

In this lesson you will learn how to multiply decimals by whole numbers 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

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Whole Unit (Ones)

Tenths

Hundredths

Let’s ReviewLet’s Review

Tenths Hundredths

Ones Tenths

Hundredths

1 2 3

1.23

1 Whole 2 3

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Multiplication is repeated addition

5 x315

3 + 3 + 3 + 3 + 3 = 15

Let’s ReviewA Common Mistake

Forgetting to take the decimal into consideration when multiplying.

0.1 x 11 ≠ 11

Let’s ReviewCore Lesson Smart Estimate7 x 0.15

7 x 0.1 is 7 tenths

7 x 0.2 is 14 tenths

14 tenths iswritten 1.4

Smart estimate:

Between 0.7 and 1.4Around 1

0.15 is halfway between 0.1 and

0.2

0.7 1.4

7

x0.15

= 7

≈ x0.1

= 7

≈ x0.2

Let’s ReviewCore Lesson 7 x 0.15

Ones Tenths

Hundredths

1 0 5

This is a reasonable

answer since it is close to my

smart estimate

Let’s ReviewCore LessonA pencil costs $0.28.

How much do 6 pencils cost?

$0.28 is close to $.25

Smart estimate: Around $1.50

$1.50

6

x0.28

= 6

≈ x0.25

Let’s ReviewCore Lesson 6 x $0.28

Ones Tenths

Hundredths

1 6 8

This is a reasonable

answer since it is close to my

smart estimate

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

area model.

Let’s ReviewGuided Practice

5 x 0.25

Let’s ReviewExtension Activities

Explain why the answer is a decimal when you multiply a whole number by a decimal.

Let’s ReviewExtension Activities

Estimate the answer and then use an area model to show the multiplication of 4 x 0.35.

Let’s ReviewQuick Quiz

Which area model shows 3 x 0.18?

A B C D