A focused Grade 3 learning session for Rounding Whole Numbers using visual models, worked examples, strategy guidance, and a short mastery check.
Student goal: I can round a whole number to the nearest 10 or 100.
Rounding Whole Numbers means using place value, operations, and equations to reason accurately with numbers.
Question: Look at the number line. The number marked \(?\) is closest to which value when rounded to the nearest \(10\)?
Why it works: The point is between \(250\) and \(255\), closer to \(250\). A number like \(251\)--\(254\) rounds to \(250\) (ones digit \(<5\)).
Answer: \(250\)
Question: Fill in the blank: \(156\) rounded to the nearest \(100\) is \_\_\_\_.
| Number | Round to 10 | Round to 100 |
|---|---|---|
| \(156\) | \(160\) | ? |
Answer: \(200\)
Question: The number shown is between \(400\) and \(500\). Is it closer to \(400\) or \(500\)?
Answer: Closer to \(500\)
Question: Two students round differently. Maria says \(127\) rounds to \(130\) (nearest \(10\)). Josh says \(127\) rounds to \(100\) (nearest \(100\)). Are both students correct? Explain.
Why it works: For \(127\): to the nearest \(10\), look at the ones digit (\(7\geq5\)), so it rounds to \(130\). To the nearest \(100\), look at the tens digit (\(2<5\)), so it rounds to \(100\). Both answers are correct for their respective place values.
Answer: Both are correct because they are rounding to different place values
Rounding Whole Numbers becomes easier when students connect the question to a model, use clear steps, and explain why the answer fits.
Understand the model before choosing the operation.
Use scratch paper. The explanation matters more than simply seeing whether the choice is correct.
What is \(367\) rounded to the nearest \(100\)?
Answer C: \(400\)
For \(367\), look at the tens digit (\(6\)). Since \(6\geq5\), round the hundreds digit up: \(367\) rounds to \(400\).
When you round \(45\) to the nearest \(10\), why does the ones digit matter more than the hundreds digit?
Answer A: Because we are rounding to the nearest \(10\), not the nearest \(100\)
When rounding to the nearest \(10\), we look at the ones digit to decide if we round up or down. The ones digit is \(5\), so \(45\) rounds to \(50\).
For a number like \(\_\_\_\), the rounding rule says "look at the tens digit." What does the rounding rule mean by "look"?
Answer D: Check whether it is \(5\) or greater to decide if we round up
In rounding, "look at the digit" means check its value to apply the rule: if it's \(5\) or more, round up; if less than \(5\), round down.
Two students round differently. Maria says \(127\) rounds to \(130\) (nearest \(10\)). Josh says \(127\) rounds to \(100\) (nearest \(100\)). Are both students correct? Explain.
Answer C: Both are correct because they are rounding to different place values
For \(127\): to the nearest \(10\), look at the ones digit (\(7\geq5\)), so it rounds to \(130\). To the nearest \(100\), look at the tens digit (\(2<5\)), so it rounds to \(100\). Both answers are correct for their respective place values.
Look at the number line. The number marked \(?\) is closest to which value when rounded to the nearest \(10\)?
Answer A: \(250\)
The point is between \(250\) and \(255\), closer to \(250\). A number like \(251\)--\(254\) rounds to \(250\) (ones digit \(<5\)).
Round \(589\) to the nearest \(100\).
Answer D: \(600\)
The tens digit is \(8\). Since \(8\geq5\), round up: \(589\) rounds to \(600\).
Round \(476\) to the nearest \(100\).
Answer D: \(500\)
The tens digit is \(7\). Since \(7\geq5\), round up: \(476\) rounds to \(500\).
Round \(92\) to the nearest \(10\).
Answer D: \(90\)
The ones digit is \(2\). Since \(2<5\), round down: \(92\) rounds to \(90\).
What is \(145\) rounded to the nearest \(100\)?
Answer A: \(100\)
The tens digit is \(4\). Since \(4<5\), round down: \(145\) rounds to \(100\).
Round \(267\) to the nearest \(10\).
Answer C: \(270\)
The ones digit is \(7\). Since \(7\geq5\), round up: \(267\) rounds to \(270\).
What is \(804\) rounded to the nearest \(10\)?
Answer A: \(800\)
The ones digit is \(4\). Since \(4<5\), round down: \(804\) rounds to \(800\).
