Multiples of 100
10 min
Narrative
The purpose of an Estimation Exploration is to practice the skill of estimating a reasonable answer, based on experience and known information. It gives students a low-stakes opportunity to share a mathematical claim and the thinking behind it (MP3). Asking yourself, “Does this make sense?” is a component of making sense of problems (MP1), and making an estimate or a range of reasonable answers, with incomplete information, is a part of modeling with mathematics (MP4).
This is the first time students experience the Estimation Exploration routine in grade 3. Students are familiar with this routine from a previous grade, but, they may benefit from a brief review of the steps involved.
Launch
- Groups of 2
- Display the image.
- “What is an estimate that’s too high? Too low? About right?”
- 1 minute: quiet think time
Teacher Instructions
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Record responses.
- “Which groups on the field did you count as part of the marching band?” (I counted only the performers in the band uniforms. I included everyone on the field.)
Student Task
How many people are in the marching band?
Record an estimate
that is:
| too low | about right | too high |
|---|---|---|
Solution Steps (4)
- 1View marching band image→Estimate how many people are in the band
- 2Give too low estimate→Less than 100 (clearly too few)
- 3Give about right estimate→140-200 (reasonable based on visible groups)
- 4Give too high estimate→More than 250 (clearly too many)
Sample Response
- Too low: less than 100
- About right: 140–200
- Too high: more than 250
Activity Synthesis (Teacher Notes)
- “Notice that many of our estimates are expressed in terms of tens and hundreds. Why might that be? Why don’t we estimate that there are about, say, 163 people or 248 people in the picture?” (If we are estimating, we aren’t trying to guess the exact number. Tens and hundreds are easy to think about.)
- “It is often helpful to get a sense of a quantity (how many, how much, how long, etc.), with groups of 10 or groups of 100. Numbers that are groups of 10, such as 50 and 90, can be called ‘multiples of 10.’ Numbers that are groups of 100, such as 200 and 700, can be called ‘multiples of 100.’”
- “When we estimate, we often name the multiple of 10, or multiple of 100, that we think the number is close to.”
- “But how do we decide whether a number is close to some multiple of 10 or some multiple of 100? We’ll think more about this question in the next activity.”
Standards
- 3.NBT.1·Use place value understanding to round whole numbers to the nearest 10 or 100.
- 3.NBT.A.1·Use place value understanding to round whole numbers to the nearest 10 or 100.
10 min
25 min
Knowledge Components
All skills for this lesson
Multiples of 100
10 min
Narrative
The purpose of an Estimation Exploration is to practice the skill of estimating a reasonable answer, based on experience and known information. It gives students a low-stakes opportunity to share a mathematical claim and the thinking behind it (MP3). Asking yourself, “Does this make sense?” is a component of making sense of problems (MP1), and making an estimate or a range of reasonable answers, with incomplete information, is a part of modeling with mathematics (MP4).
This is the first time students experience the Estimation Exploration routine in grade 3. Students are familiar with this routine from a previous grade, but, they may benefit from a brief review of the steps involved.
Launch
- Groups of 2
- Display the image.
- “What is an estimate that’s too high? Too low? About right?”
- 1 minute: quiet think time
Teacher Instructions
- “Discuss your thinking with your partner.”
- 1 minute: partner discussion
- Record responses.
- “Which groups on the field did you count as part of the marching band?” (I counted only the performers in the band uniforms. I included everyone on the field.)
Student Task
How many people are in the marching band?
Record an estimate
that is:
| too low | about right | too high |
|---|---|---|
Solution Steps (4)
- 1View marching band image→Estimate how many people are in the band
- 2Give too low estimate→Less than 100 (clearly too few)
- 3Give about right estimate→140-200 (reasonable based on visible groups)
- 4Give too high estimate→More than 250 (clearly too many)
Sample Response
- Too low: less than 100
- About right: 140–200
- Too high: more than 250
Activity Synthesis (Teacher Notes)
- “Notice that many of our estimates are expressed in terms of tens and hundreds. Why might that be? Why don’t we estimate that there are about, say, 163 people or 248 people in the picture?” (If we are estimating, we aren’t trying to guess the exact number. Tens and hundreds are easy to think about.)
- “It is often helpful to get a sense of a quantity (how many, how much, how long, etc.), with groups of 10 or groups of 100. Numbers that are groups of 10, such as 50 and 90, can be called ‘multiples of 10.’ Numbers that are groups of 100, such as 200 and 700, can be called ‘multiples of 100.’”
- “When we estimate, we often name the multiple of 10, or multiple of 100, that we think the number is close to.”
- “But how do we decide whether a number is close to some multiple of 10 or some multiple of 100? We’ll think more about this question in the next activity.”
Standards
- 3.NBT.1·Use place value understanding to round whole numbers to the nearest 10 or 100.
- 3.NBT.A.1·Use place value understanding to round whole numbers to the nearest 10 or 100.