Represent Measurement Data on Line Plots

10 min

Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for multiplying within 100 and to help students develop fluency.

When students use known multiplication facts to multiply greater numbers, they look for and make use of structure (MP7).

Launch

  • Display the first 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.

  • 3×103\times10
  • 3×133\times13
  • 6×136\times13
  • 3×263\times26
Solution Steps (4)
  1. 1
    Calculate 3×10
    →30 (known fact)
  2. 2
    Calculate 3×13
    →39 (use 3×10=30 plus 3×3=9)
  3. 3
    Calculate 6×13
    →78 (double 3×13=39)
  4. 4
    Calculate 3×26
    →78 (3×20=60 plus 3×6=18)

Sample Response

  • 30: I counted by 10. I just knew it.
  • 39: 3×10=303\times10=30. I just added 3, more groups of 3 which is 9, to make 39.
  • 78: I knew 3×13=393\times13=39, so I doubled 39 to get 6×136\times13, which is 78.
  • 78: 3×20=603\times20=60, 3×6=183\times6=18, and 60+18=7860+18=78.
Activity Synthesis (Teacher Notes)
  • “How did you use multiplication facts that you already know to find some of the other products?” (I knew that 3×103\times10 is 30, so 3×133\times13 would be 3 groups of 10 and 3 groups of 3, which is 39. Once I knew 3×133\times13, I was able to find 6×136\times13 by doubling 39, which is 78.)
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