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In this lesson, students will gain fluency with rounding numbers to the nearest 10s and 100s place. The lesson has number lines to help students understand rounding and movement to engage them.
Subject(s): Mathematics
Intended Audience: Educators
Instructional Time: 1 Hour(s) 30 Minute(s)
Keywords: rounding, 10s, 100s, estimation, tens, hundreds, place value
Instructional Design Framework(s): Learning Cycle (e.g., 5E)
Resource Collection: CPALMS Lesson Plan Development Initiative
Grade Level(s): 3
Suggested Technology: LCD Projector
Freely Available: Yes
Instructional Component Type(s): Lesson Plan
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will explain that rounding means to find the closest benchmark (friendly) number so you can replace some of the digits in a number with zero.
Students will identify opportunities when rounding numbers is appropriate.
Students will relate real world applications to the concept of rounding.
Students will use place value knowledge to round numbers to the nearest 10 or 100.
Prior Knowledge: What prior knowledge should students have for this lesson?
Students need to understand that when you move to the right across the places in a number (e.g., 567), the digits represent smaller units.
Students need to know the place values ones, tens, and hundreds.
Guiding Questions: What are the guiding questions for this lesson?
How does rounding help make math easier? (Rounding gives us less digits to work with, it is easier to combine numbers that are rounded, etc.)
Why do we round numbers? (We round numbers when we do not need an exact answer, if we are making an estimate, to see if our answer is close, etc.)
When might you use an estimation? (To see if you have enough of something, to see if you are close to a number, etc.)
Teaching Phase: How will the teacher present the concept or skill to students?
Introduce the lesson by telling students that we will be learning how to round numbers today.
Write two addition problems on the board: 28+56= and 30+60= . Take a poll of the class to decide which problem they would prefer to answer and why. Students will most likely say they would prefer to answer the 30+60= problem because it is easier and it doesn't take as much time.
Ask, "Why would we round a number instead of using the exact number?" (Possible answers: to check to see if an answer is close; if you are trying to estimate a sum or product; if you want to see if you have enough money to purchase something; etc.)
Administer the Rounding Pretest to students (see formative assessment). Students should at least be able to answer 60% of the questions accurately. If any students are unable to correctly complete the pretest to 60% accuracy, work with them in a small group to identify each number on the number line and say which end of the number line it is closest. (Ex. For number 1: find the 27 on the number line. Ask, is 27 closer to 20 or 30?)
Guided Practice: What activities or exercises will the students complete with teacher guidance?
Present the Rounding presentation.
Slide 1: Ask students to describe in their own words what it means to round a number. Possible responses include, make the last number zero, say a number that is close to the number, etc. We will want to reinforce, not a rule, but the meaning of rounding, "finding the closest benchmark (friendly) number".

Slide 2: Read the definition and examples of rounding. Call on students to give examples of numbers that they can round.
Slide 3: Discuss why we round numbers. After reading the slide together, have students pair up and discuss instances where they might need to round a number or times when rounding would make math easier. Circulate and listen to responses and have students share some of their ideas aloud.
Slide 4: Introduce the concept of "friendly numbers." Numbers that have been rounded are "friendlier" because we don't have to deal with extra digits. Friendly numbers are numbers that are close to a ten or hundred which makes it easier to work with. Note that the answer will be close, but not exact. Explain that the friendly number is the closest number ending with no ones and/or no tens.
Slide 5: Do the examples on the slide and decide which is friendlier, 0 or 10. (0 for 2 and 4, 10 for 8 and 6).
Slide 6: Have students create a T-Chart to find the friendly numbers for digits 0-9. Have them create a t-chart to decide the friendly number for each digit (whether to round up or down). See Sample T-Chart .Students will debate whether 5 is closer to 0 or 10 because it is directly in the middle. In this case, explain that there are 10 digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) that make up all of the numbers. Explain that 1-4 are closer to 0, and 6-9 are closer to 10. Mathematicians just agreed that the halfway point, 5, would round to the higher benchmark number (10). Have students create rules for rounding down and rounding up.
Slide 7: Practice finding friendly numbers using the number lines. (13 ~ 10; 18 ~ 20; 5 ~ 10; 11 ~ 10; and 2 ~ 0)
Slide 8: Continue finding friendly numbers using the number lines.
Slide 9: Let the students derive and discuss the rules for rounding. Clarify any issues that students have. You can provide students with a number line to show that even though the digit 5 is directly in the middle, mathematicians agreed to round it up.
Slide 12: Introduce the rounding rhyme with students. Repeat aloud. Ask the students to explain why this rhyme works. You may want to show the number line to help students explain why the rhyme work.
Teachers, please note : The rounding rhyme is discussed just for fun. The students should have the conceptual understanding of how and why to round before moving to this rhyme. This might now happen on this first day of working with rounding. You may need to stay with the number lines and helping students find the closest benchmark number for several days before moving to the rhyme. Also, it is more difficult to round a middle number than it is to round the largest place value.
The first rounding problems you give students should address the largest place value. Once students understand this, then you can move to rounding the middle place value.
Slides 13-17: Model how to use the rounding rhyme to round a number (72) to the nearest ten (70). Each slide walks the students through one line of the poem.
Slides 1-16: Have the class walk through the next example together (rounding 586 to the nearest 100, 600). You can read each line of the rounding rhyme aloud with students as you move through the slides
Slides 18-19: Choose students to model the examples on this slide. Have them circle the digit, underline the number to the right of it, and round up or down. This can be done on the whiteboard. During this practice, whenever possible, reinforce why the rhyme works.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the lesson?
Now that students are familiar with rounding, you will be teaching them a "game" to check for understanding. It is called, "Rounding Round and Round."
This game works best if chairs or desks are set up in a large circle. If that is not possible, decide on a direction that student traffic should flow (clockwise, to the right, etc.). Before setting up the game, have students practice moving from seat to seat in the flow that you decided on.
Print and cut out the 25 Rounding Round and Round cards . Depending on the number of students in your class, you can add or remove cards if you would like. You will place 1 card at each seat, in order. Students will choose a seat. Whichever number card is at their seat is the number they will start with (for example, if the student sits at the chair with card number 4, his or her first question will be number 4 and he or she will answer number 3 at the very end).
Decide on an appropriate time interval for each question (30 seconds to 1 minute should be plenty). Instruct students that they will have that amount of time to answer their questions, then they will all move one seat over (to the right; clockwise; or however the class is set up). Explain that if they do not have enough time to finish, they will have extra time to go back at the end, but they must continue moving.
Provide each student with a copy of the Rounding Round and Round Student Answer Sheet . Make sure that each student knows where to answer their first question
(depending on the card at their chair) and they know to go back to number one at the end of the list (unless they are number 1).
When all students have had a chance to complete each card, collect the answer sheets. If students have answered at least 20 out of 25 questions (or 80%) correctly, they have gotten a good grasp of the concept.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
Discuss the following questions with the class.
1. Why do we round? (When making an estimate; trying to compute or check an answer quickly; etc.)
2. What is the goal of rounding? (To make friendly numbers; to find the closest number with no ones and/or no tens; to estimate; to make problems easier to do)
3. What steps do we take when rounding numbers? (Think of what two friendly numbers the number lies between. Look to the right of the digit we want to round, if it's 5, 6, 7, 8, or 9 go to the higher benchmark number, if it's 0, 1, 2, 3, or 4 go to the lower benchmark number.)
Summative Assessment
Students will fill out the Rounding Round and Round Answer Sheet during the Rounding Round and Round activity. Please see the Independent Practice for these attachments. Mastery of this concept would be 20 out of 25.
Formative Assessment
Teacher will assess student prior knowledge by administering the " rounding pretest ." Students should be able to answer at least 60% of the questions accurately.
Feedback to Students
During the rounding presentation in the Guided Practice, the teacher will facilitate discussion between student pairs and in the whole group. At the end of the presentation, students will practice rounding numbers using the rounding rhyme, giving the teacher opportunities to make corrections as needed.
Accommodations:
Provide a copy of the Rounding Round and Round cards to children with special needs and allow them to write their answers directly on the card. You can print the cards as "handout - 9 slides to a page" to save paper.
Provide a number line to students to use while rounding numbers.
Extensions:
As an extension, students can solve problems rounding to the nearest thousands and ten thousands place.
Suggested Technology: LCD Projector

Special Materials Needed:
Rounding Rhyme
Rounding Round and Round Cards (1 set per class, printed and cut out)
Rounding Pretest - 1 copy per student (answer key included)
Rounding Round and Round Student Answer Sheet - 1 copy per student (answer key included)
Rounding presentation, to be displayed for the class
Whiteboard or chart paper and markers, to model and practice examples
Further Recommendations:
The Rounding Round and Round activity can be used for a variety of subjects, just replace the cards with different questions or tasks.
Make sure to practice the flow of the activity before adding the cards so students know where to go during the activity.
By Author/Submitter
This lesson addresses the Mathematical Practice Standard MAFS.K12.MP.7.1: Look for and make use of structure.
Contributed by: Jessica Whelpley
Name of Author/Source: Jessica Whelpley
District/Organization of Contributor(s): Brevard
Is this Resource freely Available? Yes
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Name
MAFS.3.NBT.1.1:
Description
Use place value understanding to round whole numbers to the nearest 10 or 100.
Name
Rounding to the Nearest
Hundred:
Name
Rounding Relay:
Description
Students round two-, three-, and four-digit numbers to the nearest hundred.
Description
This lesson uses an exciting relay game and real-life application activities to provide students will the skills necessary to round whole numbers to the nearest 10 or 100.