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Introducing the Concept

Multi-digit by One-digit Multiplication

Prior to teaching multi-digit by one-digit multiplication, students need to learn basic multiplication facts. Since children do not learn at the same rate, some of your students will need extra practice with basic multiplication facts prior to learning multi-digit multiplication. Once children have learned their multiplication facts, it is time to introduce multiplying by multiples of 10. This will allow you to develop the concept of multi-digit multiplication.

Materials: Overhead projector or chalkboard

Preparation: none

Prerequisite Skills and Concepts: Students should have mastered basic multiplication facts and multiplication by ten.

  • Write 1 x 3 on the overhead or board.

  • Ask: What is 1 x 3?
    Students should know their basic facts and quickly respond with an answer of 3.

  • Write 10 x 3 on the overhead or board.

  • Ask: What is 10 x 3? How do you know?
    Some students may say that because the product of 1 times 3 is 3, the product of 10 times 3 is 30. Other students may focus attention on the number of zeros in the factors and the product. If not, ask the following question.

  • Ask: How many zeros are in the factors? How many zeros are in the product?
    Students should observe that the number of zeros in the product is the same as the number of zeros in the factors.

  • Ask: How could you find the product of 20 x 3?
    Students should make the connection that 2 x 3 = 6, so 20 x 3 = 60.

  • Continue with additional exercises using single-digit numbers multiplied by 2-digit multiples of 10. Then extend this concept to multiplying by 3-digit multiples of 10.
    Multi-digit by one-digit:

    Properties of Multiplication:

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