Multiplication Game Day

10 min

Narrative

The purpose of this Number Talk is to elicit the strategies and understandings students have for multiplying a one-digit number and a two-digit number, which will be helpful later in this lesson when students continue to practice multiplying within 100.

Launch

  • Display one expression.
  • “Give me a signal when you have an answer and can explain how you got it.”
  • 1 minute: quiet think time
Teacher Instructions
  • Record answers and strategies.
  • Keep expressions and work displayed.
  • Repeat with each expression.

Student Task

Find the value of each expression mentally.

  • 4×104\times10
  • 4×204\times20
  • 4×214\times21
  • 4×244\times24

Sample Response

  • 40: I just knew it.
  • 80: It's twice the previous product because the 10 doubled to 20. I just knew it.
  • 84: It would be 4 more than 4×204 \times 20, so it would be 80 plus 4.
  • 96: 4×20=804\times20=80. 4×4=164\times4=16. 80+16=9680+16=96.

Synthesis

  • “How did you figure out the more challenging products?” (Once I knew 4×204\times20, I was able to build on it to find 4×214\times21 and 4×244\times24 by just adding more fours. I knew that 4 groups of 25 make 100, so I took away 4 to find 4 groups of 24.)
Standards
Addressing
  • 3.OA.7·Fluently multiply and divide within 100, using strategies such as the relationship between multiplication and division (e.g., knowing that 8 × 5 = 40, one knows 40 ÷ 5 = 8) or properties of operations. By the end of Grade 3, know from memory all products of two one-digit numbers.
  • 3.OA.C.7·Fluently multiply and divide within 100, using strategies such as the relationship between multiplication and division (e.g., knowing that <span class="math">\(8 \times 5 = 40\)</span>, one knows <span class="math">\(40 \div 5 = 8\)</span>) or properties of operations. By the end of Grade 3, know from memory all products of two one-digit numbers.

20 min

20 min