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Rounding a number means giving a number that is close to the original number based on the desired place value.
Here’s how to round a number.
Find the digit in the position you’re rounding to.
Look at the digit directly to the right.
If it’s 0, 1, 2, 3, or 4, the digit in the position you’re rounding to stays the same.
If it’s a 5, 6, 7, 8, or 9, add 1 to the digit in the position you’re rounding to.
Replace the digits to the right of the rounded digit with zeros.
If any digits to the right of the rounded digit come after a decimal point, you can delete them.
A concert at an outdoor stage attracted a crowd of 91 627 people. If we round to the nearest ten thousand, approximately how many people attended the concert?
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The digit in the ten thousands position in 91 627 is 9. |
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The digit to the right of the 9 in 91 627 is a 1, so we know that the 9 stays the same. |
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91 627 rounded to the nearest ten thousand is 90 000. |
Answer: Around 90 000 people went to the concert
Lily spent $24.88 on candy. Approximately how much money is this if we round to the nearest unit?
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The digit in the ones position in 24.88 is 4. |
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The digit to the right of the 4 in 24.88 is an 8, so we know that we have to add 1 to the number 4. 4 + 1 = 5 |
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24.88 rounded to the nearest unit is 25. |
Answer: Lily spent approximately $25 on candy
When rounding up, we need to add a carry digit if the digit in the position we’re rounding to is a 9.
For example, let’s say we want to round 297 to the nearest ten.
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The digit in the tens position in 297 is 9. |
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The digit to the right of the 9 in 297 is a 7, so we know that we have to add 1 to the number 9. 9 + 1 = 10 So, we write a 0 in the tens place and add a carry digit of +1 to the hundreds position. +1 |
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297 rounded to the nearest ten is 300. |
Rounding can be used to approximate the answer to a calculation.
For example, to find the approximate answer to a complex addition problem, we can round the numbers before adding them up.
What is the approximate sum of 120.25 and 45.89?
Before doing the calculation, we need to round both numbers to the nearest whole number.
Rounding 120.25
| The digit in the ones position 120.25 is 0. |
| The digit to the right of the 0 in 120.25 is a 2, so we know that the 0 stays the same. |
| 120.25 rounded to the nearest unit is 120,00 or simply 120. |
Rounding 45.89
| Le chiffre à la position des unités dans 450,89 est 5. |
| The digit to the right of the 5 in 45,89 is an 8, so we know that we have to add 1 to the number 5. 5 + 1 = 6 |
| 45.89 rounded to the nearest unit is 46,00 or simply 46. |
Add the rounded numbers.
120,25 + 45,89 = ?
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120 + 46 ≈ 166
Answer: The sum of 120.25 and 45.89 is approximately 166.