Lesson 4 — Activity 2: Rounding Decimal Numbers
Completion requirements
Lesson 4 — Activity 2:
Rounding Decimal
Numbers
When we talk about money, we use only two places after the decimal. However, sometimes your math questions give you answers that are three or more places after the decimal. You need to use your rounding skills to round the answer to only two places after the decimal when dealing with money!
HINT:
If the number to the right of your number is less than 5 (0, 1, 2, 3, or 4), the original number stays the same. But, if the number to the right of the number you need to round is equal to 5 or greater (5, 6, 7, 8, or 9), you round your number up one digit.
It does not matter if there is a decimal point. The rounding rules always remain the same.
Examples:
4.7 rounds to 5.0
4.3 rounds to 4.0
4.75 becomes 4.8
4.37 become 4.4
Rounding a number to the nearest tenth:
Example: 0.72
1. Find the place value to be rounded (in this case, to the nearest tenth): 0.72.
2. Look at the digit to the right of the number that you are rounding to: (in this case, the 2): 0.72.
a. If the highlighted digit is 4 or less, round down. This means that the number in the tenths
column
stays as is.
b. If the highlighted digit is 5 or greater, round up. This means that the number in the tenths
column
must go up by 1.
3. In this number, the digit to the right of 7 is 2, which is less than 5, so you must round down. This means that 7 in the tenths
column
stays at 7.
a. If the highlighted digit is 4 or less, round down. This means that the number in the tenths column stays as is.
b. If the highlighted digit is 5 or greater, round up. This means that the number in the tenths column must go up by 1.
4. The last step is to write the rounded number: 0.7.
5. You’re done!
Rounding a number to the nearest hundredth:
Example: 0.687
1. Find the place value to be rounded (in this case to the nearest hundredth): 0.687.
2. Look at the digit to the right of the number that you are rounding to (in this case, the 7): 0.687.
a. If the highlighted digit is 4 or less, round down. This means that the number in the hundredth column stays as is.
b. If the highlighted digit is 5 or greater, round up. This means that the number in the hundredth column must go up by 1.
3. In this number, the digit to the right is 7, which is greater than 5, so you must round up. This means that the 8 in the hundredths column goes up to 9.
4. The last step is to write the rounded number : 0.69.
5. You’re done!
Click here to download a document that will show you step by step how to round decimals using a number line!
Self-check!
Try this!
Answer these questions on your own first.
When you are finished, click on the tab below to check your answers!
Round these numbers to two places, or the hundredths place after the decimal:
$35.784
$23.729
Round these numbers to the nearest dollar:
$235.60
$723.47
