4th Grade Rounding Whole Numbers Lesson (Free PDF)
Rounding replaces a number with the closest multiple of a place, such as ten, hundred, or thousand. Look at the digit to the right of that place. If it is 5 or more, round up. If it is 4 or less, keep the digit. Then change the digits to its right to zeros. Rounding also helps estimate sums and differences.
Grade 4 · Common Core State Standards: 4.NBT.A.3
- To round, look at the digit to the right of the place you want.
- Digits 5, 6, 7, 8, and 9 round up. Digits 0, 1, 2, 3, and 4 round down.
- A number exactly halfway between two multiples rounds up: 2,500 rounds to 3,000.
- A 9 can carry: 9,960 rounds to 10,000 at the nearest hundred.
- To estimate, round every number to the same place, then add or subtract.
What does rounding mean?
Rounding swaps an exact number for a nearby, friendlier number. Newspapers say “about 19,000 fans” instead of “18,743 fans.” Rounding makes numbers easy to say, compare, and add in your head.
How do you round a whole number?
- Underline the digit in the place you are rounding to.
- Look at the digit to its right.
- If that digit is 5 or more, add 1 to the underlined digit. If it is 4 or less, keep the underlined digit.
- Change every digit to the right of the underlined place to 0.
Example: Round \(38,745\) to the nearest thousand. The underlined digit is 8 (thousands). The digit to its right is 7, which is 5 or more, so 8 becomes 9. The answer is \(39,000\).
Does the place you pick change the answer?
Yes. A smaller place keeps more detail. A bigger place gives a rougher answer.
Watch for a 9. Rounding \(9,960\) to the nearest hundred gives \(10,000\), because 99 hundreds plus 1 more hundred is 100 hundreds.
How can rounding help you estimate?
To estimate a sum or a difference, round each number first, then add or subtract. Use the same place for every number so the problem is easy.
The exact sum is \(7,001\), which is close to the estimate of \(7,000\). If your exact answer is far from your estimate, check your work again.
Questions about rounding whole numbers
What is the rule for rounding up?
Round up when the digit to the right of the rounding place is 5 or more. Add 1 to the digit in the rounding place and change the digits to its right to zeros.
What does 2,500 round to at the nearest thousand?
It rounds to 3,000. The number is exactly halfway between 2,000 and 3,000, and the rule is to round halfway numbers up.
Why do we round numbers?
Rounded numbers are easier to compare and calculate in your head. They are good for estimates, such as checking that a total on a receipt makes sense.
How do you estimate a sum with rounding?
Round each number to the same place, then add. To estimate 4,862 + 2,139, round to the nearest thousand and add 5,000 + 2,000 = 7,000.
What happens when you round 999 to the nearest ten?
The answer is 1,000. The ones digit 9 rounds the 9 tens up to 10 tens, which carries into the hundreds and thousands.
All Grade 4 chapters: Grade 4 math.
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