Often in math, it is difficult to work with large or complex numbers. When you don't need an accurate answer, but just an estimation, rounding is a useful practice. Rounding makes numbers easier to work with by reducing the digits in the number while keeping the value similar to the original number. You can round a number to any place value depending on how much you want to change the original value of the number. The rounded number can then be used in the math problem to get an approximate answer.
Determine which place value you are going to round the number to. Underline the digit in the place value position you will round to. For example, if you want to round to the nearest hundred, underline the digit in the hundreds place. When rounding the number 2,365 to the nearest hundred, underline the 3 because it is in the hundreds place.
Look at the digit to the right of your underlined numeral. Determine if it is greater than or equal to 5. If so, you will round your underlined digit up. If the digit to the right of your underlined numeral is less than 5, you will round your number down. In the example 2,365 you are rounding to the nearest hundred, so look at the digit to the right of the hundreds place, which is 6. Since this is greater than 5, you will round up.
When rounding up, add 1 to your underlined numeral and then change all of the digits to the right of the underlined numeral to zeros. In the example 2,365 when rounding to the nearest hundred, you would change the 3 to a 4 and change the 6 and 5 to zeros, so your rounded number would be 2,400.
When rounding down, the underlined numeral stays the same and all of the digits to the right of it change to zeros. For example, if you are rounding the number 4,623 to the nearest hundred, you would end up with 4,600 because the digit to the right of the hundreds place is less than 5.
Tips & Warnings
- Make sure you are underlining the correct place value in your number when rounding, especially if you are working with decimals. If you are asked to round to the nearest hundredth, you will have a much different result than rounding to the nearest hundred.
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