Round to Hundred

Overview

Lesson 8 of 18 in the unit Math in Our World. Students use a number line and place-value reasoning to round whole numbers to the nearest hundred, then apply the skill independently and explain how the tens digit determines the estimate.

Learning intentions

Students will be able to:

• I can identify the hundreds and tens digits in a number.
• I can round a number to the nearest hundred.
• I can use a number line to decide which hundred is closest.
• I can explain why the tens digit helps me choose the answer.

Success criteria

• I check the tens digit.
• I round down when the tens digit is 0–4.
• I round up when the tens digit is 5–9.
• I write zeros in the tens and ones places.

Curriculum links

• Operations and Algebraic Thinking — solve two-step problems and assess whether answers are reasonable using estimation, including rounding.
• Measurement and Data — apply mathematical reasoning to real-world problems and communicate solutions clearly.
• Place value and estimation — use the relationship between hundreds and tens to make reasonable estimates.

Lesson structure (30 minutes)

1. 0–3 min · Hook and connect. Teacher displays 349 and 351 on the opening number-line question and asks, “Which number is closer to 400? How do you know?” Students quietly estimate, show a thumb choice, and briefly explain their thinking.

2. 3–8 min · Model the number line. Teacher uses the number-line model to place 149 between 100 and 200, marking the midpoint at 150; model that 149 rounds to 100 because it is closer to 100. Point out the bold hundreds and tens labels and state: “The tens digit tells us whether to stay at the lower hundred or move to the next hundred.” Students identify the nearest hundred and repeat the rule using oral responses, pointing, or mini whiteboards.

3. 8–15 min · Guided examples. Teacher models 350 and 782, thinking aloud: underline the tens digit, compare it with 5, and replace the smaller places with zeros. Students help complete each example and then use the guided practice slides to drag or point to numbers on a number line, choose the closest hundred, and move a 0 card into the tens and ones places. Check each student’s reasoning before revealing the answer.

4. 15–20 min · Partner practice. Teacher gives each pair a turn with the rounding practice and assessment sheet and reads the short directions aloud. Students round six numbers to the nearest hundred, first using a number line when needed and then recording the hundreds, tens, and ones digits; partners take turns explaining, “The tens digit is __, so I round __.”

5. 20–27 min · Individual assessment. Teacher asks students to complete the five three-choice questions on the rounding practice and assessment sheet independently, including numbers such as 149, 350, and 782. Students circle one answer for each question and may respond orally or by pointing if writing is a barrier; teacher quietly checks that each student identifies the tens digit rather than guessing.

6. 27–30 min · Review and close. Teacher revisits the rule and final check slide and asks students to explain why 450 rounds to 500 and 441 rounds to 400. Students share one “I can” statement and show a final response for 650: 600 or 700, with a brief justification.

Resources

• the rounding-to-the-nearest-hundred slide deck
• the rounding practice and assessment sheet
• Five mini whiteboards or paper response boards
• Number-line display from 0 to 1,000 with marked hundreds
• Place-value cards labeled hundreds, tens, and ones
• 0 cards for replacing smaller places
• Pencils and highlighters
• Optional device or interactive display for dragging numbers

Assessment

• During modeling, ask each student to identify the tens digit and predict whether the number rounds up or down.
• During guided and partner practice, listen for the rule “0–4 stays; 5–9 goes up” and check that zeros replace the tens and ones places.
• Score the five-question individual check: 4–5 correct indicates secure understanding; 2–3 suggests targeted reteaching; 0–1 requires concrete number-line support.

Differentiation

• Support students with a high-contrast hundreds number line, visual benchmarks, bold place labels, and a highlighted tens digit. Begin with numbers between 100 and 300 before using the full range to 1,000.
• Give short, one-step directions and read every question aloud. Offer oral, pointing, or selected-response answers for students with dyslexia, fine-motor needs, or writing difficulties.
• Use a sentence frame: “The tens digit is __. It is [less than/at least] 5, so __ rounds to __.”
• For students ready for more challenge, include mixed-place comparisons such as rounding 782 to the nearest ten and nearest hundred, then ask which estimate is more precise and why.