Scaled Picture Graphs

10 min

Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for adding within 100. These understandings help students develop fluency and will be helpful later in this lesson when students need to add to find the total number of students represented in a picture graph. When students use strategies based on place value to add, they look for and make use of structure (MP7).

This is the first time students experience the Number Talk routine in IM Grade 3. Students should be familiar with this routine from a previous grade. However, they may benefit from a brief review of the steps involved.

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.

  • 50+1050 + 10
  • 50+1250 + 12
  • 60+1360 + 13
  • 65+1365 + 13
Solution Steps (4)
  1. 1
    Compute 50 + 10 mentally
    →5 tens + 1 ten = 6 tens = 60
  2. 2
    Compute 50 + 12 mentally
    →5 tens + 1 ten = 6 tens, plus 2 ones = 62
  3. 3
    Compute 60 + 13 mentally
    →6 tens + 1 ten = 7 tens, plus 3 ones = 73
  4. 4
    Compute 65 + 13 mentally
    →6 tens + 1 ten = 7 tens, 5 ones + 3 ones = 8 ones = 78

Sample Response

  • 60: 5 tens and 1 ten make 6 tens, which is 60.
  • 62: It’s just like the first one, but there are 2 ones, so it is 62.
  • 73: It’s like the second problem, but there’s 1 more ten and 1 more one. So each digit goes up by 1 and that’s 73.
  • 78: There are 7 tens and 8 ones, so it’s 78.
Activity Synthesis (Teacher Notes)
  • “How was place value helpful as you added these numbers?” (I was able to use tens and ones to help me find the sum.)
  • Consider asking:
    • “Who can restate _____’s reasoning in a different way?”
    • “Did anyone use the same strategy but would explain it differently?”
    • “Did anyone approach the problem in a different way?”
    • “Does anyone want to add on to _____’s strategy?”
Standards
Building On
  • 2.NBT.5·Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
  • 2.NBT.B.5·Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

15 min

20 min