A multi-day mathematical journey for elementary learners to master rounding whole numbers to the nearest ten. Students transition from concrete visual number lines and benchmark midpoint reasoning to multi-digit place value strategies and real-world estimation problem solving.
Park logbook rounded estimate: Maya should record: miles
How confident do you feel rounding 2-digit numbers?
Need Help Getting It Trail Master!
Benchmark Bounds • Grade 3 Math Page 2 of 2
85
80
85
90
90
93
90
95
100
90
Part 4: Multiple Choice Solutions (2 pts each)
11. Which number does NOT round to 50?
Correct Choice: C (55) 55 rounds UP to 60.
12. Midpoint between 80 and 90:
Correct Choice: B (85) Midpoints always end in 5.
Part 5: Word Problem Solution (3 pts total)
13. Maya's 47-mile hike rounded to the nearest ten:
Final Answer: Maya should record 50 miles in the logbook.
Model Student Work & Justification:
Benchmark tens: 40 and 50.
Midpoint between 40 and 50: 45.
47 is 2 units greater than 45, making it closer to 50 than to 40 (only 3 miles from 50 vs. 7 miles from 40).
Rubric Breakdown: 1 pt for stating 50 miles, 1 pt for identifying benchmark tens (40/50) or midpoint (45), 1 pt for accurate explanation or number line drawing.
Target Tens Key • Lesson 1 Page 2 of 2
825
• 824 is to the left of 825 → Rounds to 820.
Example B: 395 (Century Rollover)
• Benchmark tens: 390 and 400
• Midpoint: 395
• Lands on midpoint → Rounds UP to 400.
Formative Check: Ask students: "Why does 400 have two zeroes even though we rounded to the nearest ten?" (Because 10 tens equals 1 hundred!).
04
Independent Application (15 Mins)
Students complete the Triple Digit Tens Worksheet individually or in pairs.
Circulation Focus: Watch for students changing the hundreds digit when rounding numbers like 523 (e.g., mistakenly writing 600 or 500).
Frequent 3-Digit Pitfalls
Error
What the Student Did
Intervention Script
Dropping the Hundreds
Rounded 746 to 50 instead of 750.
"You rounded the tens place correctly, but don't forget the 7 hundreds waiting in line!"
Rounding to 100 instead of 10
Rounded 482 to 500 instead of 480.
"Nearest ten means benchmark multiples like 470, 480, 490. You only zero out the ones place."
9-Rollover Freeze
Wrote "190" for 198 rounded to nearest 10.
"198 is only 2 away from 200! When 9 rounds up, 19 tens becomes 20 tens (200)."
Tier 2 Support
Provide a physical "Place Value Window Card" with a slider hole that frames only the tens and ones places while the hundreds remain in view.
High-Flyer Challenge
"Find the smallest and greatest 3-digit whole number that each round to 640 when rounded to the nearest ten." (Smallest: 635; Greatest: 644).
Target Tens Sequence • Lesson 2 of 3 Page 2 of 2
753
50
What did Chloe do wrong?
Correct Answer:
Part 5 Expedition Logistics Word Problem
Supply Cans: Camp Ranger Marcus ordered 384 cans of trail mix for the summer base camp. For easy packing, he groups them into cartons of 10. To find out approximately how many cans he ordered, round 384 to the nearest ten.
Show your thinking above. Marcus ordered about: cans
Triple Digit Tens • Grade 3 Math Page 2 of 2
Case #2: Chloe (753 → 50)
Student Explanation: Chloe dropped the hundreds place completely. 753 has 7 hundreds, so the rounded number must still have 7 hundreds (750).
Correct Answer: 750
Part 5: Supply Cans Solution (3 pts total)
Round 384 cans to the nearest ten:
Final Answer: Marcus ordered approximately 380 cans.
Mathematical Justification:
1. Target place is tens (8 tens = 80).
2. The ones place digit is 4.
3. Because 4 is less than 5, 384 is closer to 380 than 390 (4 away from 380 vs. 6 away from 390).
Target Tens Key • Lesson 2 Page 2 of 2
Station 2: Mystery Code Breaker
Students analyze clues combining rounding constraints with odd/even properties and digit sums to deduce secret camp lock combinations.
04
Expedition Debrief & Exit Check (10 Mins)
Synthesis Question:"If you round two numbers before adding them, will your estimated sum always be higher than the exact answer? Why or why not?"
Key takeaway: It depends! If one number rounds up and the other rounds down, their rounding differences balance out.
Unit Mastery Assessment Matrix
Level
Performance Criteria
Next Step
4 - Trail Master
Accurately rounds any 2- or 3-digit number to nearest 10, including century rollovers (e.g. 798 → 800), and justifies reasonableness of estimates.
Advance to rounding to nearest 100.
3 - Proficient
Rounds standard 2- and 3-digit numbers correctly using midpoints; minor calculation error when 9 is in tens place.
Practice century crossover drills.
2 - Developing
Rounds 2-digit numbers with visual number line; confuses rounding to nearest 10 with nearest 100 on 3-digit numbers.
Use Place Value Zoom Lens strip.
1 - Emerging
Struggles to identify surrounding benchmark tens; chooses non-multiples of ten as rounded values.
Return to Lesson 1 Hill Model.
Target Tens Sequence • Lesson 3 of 3 Page 2 of 2
My digits add up to 14.
What secret number am I?
Summit Challenge: The Ranger's Supply Route
A rescue team is packing protein bars. Box A has 187 bars and Box B has 214 bars. Before setting off, the team leader estimates total bars by rounding each box to the nearest ten.
Estimated bars: Exact bars: Difference between exact & estimate:
Final Trail Exit Check:
A. Round 796 to the nearest ten:
Answer:
B. Name the greatest number that rounds to 80:
Answer:
Estimation Station • Grade 3 Math Page 2 of 2
401 bars
Difference:
1 bar
Part 5: Exit Check Key (3 pts total)
A. Round 796 to nearest ten:
Answer: 800
Century rollover: 79 tens + 1 ten = 80 tens (800).
B. Greatest number rounding to 80:
Answer: 84
85 is midpoint and rounds up to 90; thus 84 is max.
