Multidigit by One-Digit Multiplication

Introduce students to this topic by showing them how they can use the properties and rules they learned with basic multiplication facts for multiplying with two-and three-digit factors.

Materials: none

Preparation: none

Prerequisite Skills and Background: Students should know the basic multiplication facts.

• Ask: When 0 is a factor in a multiplication sentence, what is the product?
  Students should know that the product is always 0.

• Ask: What is the product of 0 and 58? (0) What is the product of 967 and 0? (0) What is the product of 0 and $3.98? (0)
  Have students suggest other examples of multiplying with 0 and a two- or three-digit number as the factors.

• Ask: When 1 is a factor in a multiplication sentence, what is the product?
  Students should know that the product is always equal to the other factor.

• Ask: What is the product of 77 and 1? (77) What is the product of 1 and 365? (365) What is the product of $9.61 and 1? ($9.61)
  Have students suggest other examples of multiplying with 1 and a two- or three-digit number as the factors.

• Ask: When a factor is doubled, what happens to the product?
  Students should recall that the product is doubled.

• Write 7 3 = n on the board.

• Ask: What is the product of 7 and 3? (21)
  Replace n with 21.

• Ask: What number is double 7? (14)

• Write 14 3 = n on the board.

• Ask: What is double 21? (42) So what is the product of 14 and 3? (42)
  Replace n with 42.

• Write 16 5 = n on the board.

• Ask: How can we use doubles to find the product of 16 and 5?
  Elicit from students that 16 is double 8, 8 5 = 40, 80 is double 40, so 16 5 = 80. Replace n with 80.

• Ask: What does the Commutative Property of Multiplication tell us?
  Changing the order of the factors does not change the product.

• Write 5 16 = n on the board.

• Ask: What is the product of 5 and 16? (80)
  Replace n with 80.

• Provide students with additional examples of using doubles and the Commutative Property to multiply with two- and three-digit factors. This will help students see that multiplying with two- and three-digit factors is really not a new concept; it is just building on previously learned skills.