Learn on PengienVision, Mathematics, Grade 4Chapter 4: Use Strategies and Properties to Multiply by 2-Digit Numbers

Lesson 1: Multiply Multiples of 10

Property.

Section 1

Multiplying Using Unit Form

Property

To multiply numbers in unit form, multiply the digits and then multiply the place value units.

(a tens)×(b tens)=(a×b) hundreds(a \text{ tens}) \times (b \text{ tens}) = (a \times b) \text{ hundreds}
(a tens)×(b ones)=(a×b) tens(a \text{ tens}) \times (b \text{ ones}) = (a \times b) \text{ tens}

Examples

Section 2

Multiply Multiples of 10 by Decomposing Factors

Property

To multiply two-digit multiples of 10, you can decompose each number, then use the associative property to regroup the factors.

(a×10)×(b×10)=(a×b)×(10×10)(a \times 10) \times (b \times 10) = (a \times b) \times (10 \times 10)

This is the same as multiplying the units: a tens×b tens=(a×b) hundredsa \text{ tens} \times b \text{ tens} = (a \times b) \text{ hundreds}.

Examples

Section 3

Multiplying When the Basic Fact Ends in Zero

Property

When multiplying multiples of 10, first find the product of the basic fact. Then, annex (attach) all the zeros from the original factors to the end of that product, even if the product of the basic fact already ends in a zero.

Examples

Lesson overview

Expand to review the lesson summary and core properties.

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Section 1

Multiplying Using Unit Form

Property

To multiply numbers in unit form, multiply the digits and then multiply the place value units.

(a tens)×(b tens)=(a×b) hundreds(a \text{ tens}) \times (b \text{ tens}) = (a \times b) \text{ hundreds}
(a tens)×(b ones)=(a×b) tens(a \text{ tens}) \times (b \text{ ones}) = (a \times b) \text{ tens}

Examples

Section 2

Multiply Multiples of 10 by Decomposing Factors

Property

To multiply two-digit multiples of 10, you can decompose each number, then use the associative property to regroup the factors.

(a×10)×(b×10)=(a×b)×(10×10)(a \times 10) \times (b \times 10) = (a \times b) \times (10 \times 10)

This is the same as multiplying the units: a tens×b tens=(a×b) hundredsa \text{ tens} \times b \text{ tens} = (a \times b) \text{ hundreds}.

Examples

Section 3

Multiplying When the Basic Fact Ends in Zero

Property

When multiplying multiples of 10, first find the product of the basic fact. Then, annex (attach) all the zeros from the original factors to the end of that product, even if the product of the basic fact already ends in a zero.

Examples