Round to the Nearest Ten

Overview

In Lesson 7 of 18 in Math in Our World, students learn to round two- and three-digit whole numbers to the nearest ten. They build on place-value understanding by locating numbers on a number line, identifying the ones digit, and using rounding to estimate.

Learning intentions

• Students will be able to round whole numbers to the nearest ten.
• Students will be able to use a number line to find the closest ten.
• Students will be able to explain how the ones digit helps them round.
• Students will be able to use rounding to make a reasonable estimate.

Success criteria

• I can find the ones digit.
• I can identify the two tens numbers a number is between.
• I can choose the closest ten using a number line.
• I can explain: “5 or more, raise the score; 4 or less, let it rest.”

Curriculum links

• Georgia Grade 3 Number and Operations in Base Ten: round whole numbers to the nearest ten or hundred.
• Place value and estimation: use the ones digit to determine the nearest ten.
• Operations and Algebraic Thinking: use efficient mental strategies and explain mathematical reasoning.
• Measurement and Data: connect rounding and estimation to solving real-world problems.

Lesson structure (30 minutes)

1. 0–3 min · Hook and goal. Teacher displays a picture of a school fundraiser labeled “34 items” and asks, “Is 34 closer to 30 or 40?” using the opening estimation slide; students make a quick choice, explain their thinking to a partner, and read the “I can” goal aloud.

2. 3–15 min · I do: model rounding. Teacher uses the number-line modeling slides to place 34 between 30 and 40, demonstrates a number-line jump with counters and arrows, and models the rule “5 or more, raise the score; 4 or less, let it rest”; students track the jumps, identify the ones digit, and rehearse the rule orally.

Model a second example, such as 67. Emphasize that 67 is 3 away from 70 and 7 away from 60, so 67 rounds to 70. Briefly model 245 by locating it between 240 and 250. Ask: “What digit tells us whether to move up or stay?”

3. 15–20 min · We do: interactive number line. Teacher displays a large number line on the guided practice slides and invites students, one at a time, to move a number marker to the correct location and select the nearest ten; students solve and explain numbers such as 21, 35, 62, and 245, while classmates show thumbs-up or suggest a correction.

Use physical number lines and begin with numbers ending in 1–5. Rehearse complete responses: “The ones digit is __. The number is closer to __, so it rounds to __.”

4. 20–26 min · You do: independent practice. Teacher distributes the rounding practice worksheet and provides a mat or physical number line as needed; students round six two- and three-digit numbers, including 34, 67, 125, 238, 245, and 391, then circle or write the nearest ten.

Pause after the first problem for a quick check: students point to the ones digit and name the two possible tens. Circulate and ask, “How do you know?” without supplying the answer.

5. 26–30 min · Assessment and close. Teacher gives each student a five-question, three-choice exit check using the five-question rounding check and revisits the closing reflection slide; students independently round numbers such as 34, 67, 145, 245, and 372, then share one strategy they used.

Resources

• the complete rounding slide deck
• the rounding practice worksheet
• Large classroom number line
• Individual physical number lines or rounding mats
• Counters and arrow markers
• Dry-erase boards and markers
• Pencils and crayons
• Five-question, three-choice assessment

Assessment

• During modeling and guided practice, check whether students can identify the ones digit, locate a number between two tens, and justify the closest ten.
• Review the six practice problems for correct rounding and explanations; conference briefly with students who rely on guessing or confuse the tens and ones digits.
• Use the five-question check as the exit assessment. Students demonstrate mastery by correctly answering at least four questions and explaining one answer using the ones digit or number line.

Differentiation

• Support students with large physical number lines, counters, color-coded target tens, and numbers ending in 1–5 before introducing numbers ending in 6–9. Keep one problem per page or display only one problem at a time.
• Provide the oral sentence frame: “The ones digit is __. It is __, so I round __ to __.” Read directions and questions aloud, and allow students to answer orally or point before writing.
• For dyslexia-friendly access, use a clear sans-serif font, large numerals, strong color contrast, uncluttered pages, and a read-aloud option. Avoid requiring students to copy lengthy directions.
• Challenge students to round four-digit numbers to the nearest ten and explain why a number ending in 5 rounds up. Ask them to create a number that rounds to a selected ten.