Rounding Whole Numbers
Learn how to round whole numbers to the nearest ten, hundred, or thousand.
Definition
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Worked Examples
Round to the nearest ten.
Find the tens place
In , the tens digit is → Tens place =
Look at the digit to the right (ones place)
The ones digit is → Check digit =
Apply the rounding rule
Since , we round UP → Round up
Round up to the next ten
tens becomes tens, ones become →
Answer: rounded to the nearest ten is .
Common Mistakes
Looking at the wrong digit when rounding
Why it's wrong: Students sometimes look at the digit IN the rounding place instead of the digit to its RIGHT.
Correct: Always look at the digit ONE PLACE TO THE RIGHT of where you're rounding. For rounding to tens, look at the ones digit.
Forgetting to change digits to the right to zeros
Why it's wrong: When rounding to hundreds, some write instead of .
Correct: After rounding, ALL digits to the right of the rounding place become zeros.
Rounding down when the digit is exactly 5
Why it's wrong: Some students think 5 is 'in the middle' so it could go either way.
Correct: The rule is '5 or more, round up.' The digit 5 ALWAYS means round up.
Interactive Visual
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Interactive Sandbox
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History
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Practice Problems
15 problemsRound to the nearest ten.
Why It Matters
- Shopping: Estimating if you have enough money for items costing 24, 18, and 33 dollars (roughly 20 + 20 + 30 = 70 dollars)
- Time: Saying a trip takes "about 2 hours" instead of 1 hour and 52 minutes
- Population: Saying a city has "about 500,000 people" instead of 487,293
- Cooking: Buying "about 3 pounds" of apples instead of exactly 2.73 pounds
Real World Applications
Estimating Shopping Totals
Round prices to quickly estimate if you have enough money.
Example:
Items cost 23 dollars, 47 dollars, and 31 dollars. Round each: 20 + 50 + 30 = about 100 dollars total.
You're buying school supplies: a notebook for 7 dollars, pens for 4 dollars, and a backpack for 38 dollars.
Round each price to the nearest ten and estimate the total.
Step 1: Write the mathematical expression
Round and add: ?, ?, ?
Reporting Large Numbers
News and statistics often use rounded numbers for clarity.
Example:
A concert had 23,847 attendees. The news reports 'about 24,000 people attended.'
A school has exactly 1,247 students enrolled.
How would you report this to the nearest hundred?
Step 1: Write the mathematical expression
Round to the nearest hundred
Key Takeaways
- 1Rounding replaces a number with a simpler, nearby number
- 2Look at the digit to the RIGHT of the place you're rounding to
- 3If that digit is 5 or more, round UP. If it's 4 or less, round DOWN
- 4After rounding, all digits to the right become zeros
- 5Rounding helps with estimation and makes mental math easier