Math Help: How to Round Decimals and Whole Numbers
Elementary students begin learning to round whole numbers in 3rd grade, and they master the skill of rounding decimals in 5th grade. For a stepbystep guide to rounding, read on!
How to Round Numbers
You can round numbers when you don't need a precise answer. We often use rounding when dealing with money. For example, if you owe someone $1.99, you might just give them $2.00 if neither of you has any change. Or, if you owed someone $1.03, they might just accept a dollar if you didn't have three cents.
Whole Numbers
To round a whole number like 43 or 127, start by looking at the digit in the ones place (the last digit to the right). If the number is five or higher, you'll round the number up. If it's four or lower, you'll round the number down.
Rounding Up
To round up, change the digit in the ones place to zero. Then, find the number in the tens place (it's one digit to the left of the ones place) and add one. For instance, since the number in the tens place of 127 is two, you'll change it to three and replace the seven with zero. The result is 130.
Rounding Down
If you're rounding down, simply change the number in the ones place to zero, and leave the rest of the number alone. For example, 43 would become 40, and 111 would become 110.
Using a Number Line
You can also think of rounding as finding the closest number on the number line. For example, 127 is in between 130 and 120 on the number line, but it's closer to 130. Likewise, 43 is closer to 40 than 50. Although numbers that end in five are technically at the midpoint between two baseten numbers, they are traditionally rounded up.
Decimals
Closest Whole Number
Remember that decimals can also be found on the number line. If you're asked to round a decimal to the nearest one, you'll round it to the closest whole number. Numbers with decimals that are 0.5 or greater are rounded up, and those with decimals that are less than 0.5 are rounded down. Here are some examples:
3.7 rounds to 4.0
3.2 rounds to 3.0
3.5 rounds to 4.0
Nearest Tenth or Hundredth
You may also be asked to round decimals to the nearest tenth or hundredth. In this case, the same rules you followed for rounding whole numbers apply. If the last digit is five or greater, round up; if it's less than five, round down. The only difference is that you delete the last digit instead of replacing it with zero. Here are a few examples:
2.58 rounds to 2.6
2.54 rounds to 2.5
2.569 rounds to 2.57
2.563 rounds to 2.56
Other Articles You May Be Interested In

The decimal numbering system is the basis for modern number theory. Read on to learn how to help your children understand decimal places, percentages, and place values.

Prime numbers are positive integers that have fascinated people for thousands of years. If your child struggles to grasp prime numbers, it may help to gain a deeper understanding of how they're defined. Your child may also benefit from knowing how to identify them and how they're useful in nature.
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