Sometimes, we see problems where there are multiple digits after the decimal point. These numbers are easier to work with if they are rounded. Here's the rule for rounding up a decimal number-if the digit beside the number is 5 or more, you round up the number by 1 more. You can round up a hundredths number by 1 hundredth if the digit after the number is 5 or more. It's the same with a tenths number. If the digit beside the tenths number is 5 or more, you can round up the tenths number by 1 tenth.
Let's look at this example:
12.346758
Your teacher asks you to round off to the nearest hundredths. What is the hundredths number in this example?
12.346758
The hundredths number is 4. What digit is beside 4? It's 6 thousandths.
12.346758
We know 6 is greater (larger) than 5. We round up our hundredths number from 4 to 5. The answer is 12.35.
Let's try this number:
12.362
We are going to round off to the nearest hundredths. Can we round up our hundredths number, which is 6? Is the digit beside 6 equal to or greater (larger) than 5?
12.362
If the answers are no, we keep our original hundredths number. We remove the numbers after our hundredths number. So our final answer is 12.36.
Now let's round off to the nearest tenth using the two examples above. What is the tenths number in the first example?
12.346758
The tenths number is 3. What digit is beside 3? It's the hundredths number, which is 4.
12.346758
We know 4 is not equal to or greater than 5, so we don't round up. Our answer is 12.3.
In our second example, our tenths number is also 3. The digit beside our tenths number is 6.
12.362
Can we round up our tenths number? We can, because our hundredths number is 6. It is greater than 5. Our final answer is 12.4.
