Multiplication Practice

10 min

Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for multiplying within 100 with one factor larger than 10. These understandings help students develop fluency and will be helpful when students find factor pairs of numbers later in the lesson.

In this activity, students have an opportunity to look for and make use of structure (MP7) as they use a combination of products of smaller factors to find products of larger factors.

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 strategy.
  • Keep expressions and work displayed.
  • Repeat with each expression.

Student Task

Find the value of each expression mentally.

  • 10×610 \times 6
  • 3×63 \times 6
  • 13 ×613 \times 6
  • 12×412 \times 4

Sample Response

  • 60: I just know it. It’s 10 groups of 6.
  • 18: I just know it.
  • 78: 10×6=6010 \times 6 = 60 and 3×6=183 \times 6 = 18. So, I can just add 60+18=7860 + 18 = 78, since that’s 13 groups of 6.
  • 48: I know that 10×4=4010 \times 4 = 40 and 2×4=82 \times 4 = 8, so it’s 40+8=4840 + 8 = 48. I know that 12×2=2412 \times 2 = 24 and I can double that.
Activity Synthesis (Teacher Notes)
  • “How can knowing the value of the first two expressions help you find the value of the third expression?” (I can multiply in parts and add the smaller parts together to find a larger product.)
Standards
Building On
  • 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.

15 min

20 min