Introduction
In this lesson, you will learn how to round a number to the nearest whole number.
This video illustrates the lesson material below. Watching the video is optional.
Decimal Point
A decimal point separates a whole number from the number fragment. Anything after a decimal point is part of a number, not an entire number. Sometimes, you do not want to have the parts of a whole number, you just want to estimate the nearest whole number. Estimating is called rounding.
Figure 1
Rounding
Sometimes in life, you can’t use decimals. For example, the number of people you are inviting to a party can’t be a decimal number. You can’t have 8.7 people, but you can have 8 or 9 people. Rounding to the nearest whole number is how you deal with problems like this.
The table below shows the rules for whether you round down (for example, from 17.4 to 17) or up (for example, from 17.5 to 18).
Tenths Place | How to round to nearest whole number or integer | Example |
0, 1, 2, 3, 4 | Keep the number in the one's place | 17.4 Rounds to 17 -3.4 rounds to -3 |
5, 6, 7, 8, 9 | Increase the number in the one's place by 1 | 17.5 Rounds to 18 -1.6 Rounds to -2 |
When rounding to the nearest whole number, look to the tenths place to know where to go. If the tenths place is closer to 0, round down. If the tenths place is closer to 9, round up.
Remember: The place after the decimal is the tenths place.
Example 1
Figure 2
Figure 2 shows 1.3 on a number line. To round to the nearest whole number, determine if 1.3 is closer to 2 or 1. Since 1.3 is closer to 1, you will round this number down to 1.
Example 2
Figure 3
Figure 3 shows 1.6 on a number line. Because 1.6 is closer to 2 than to 1, the estimate is 2. According to the rule outlined in the table above, the 6 in the tenths place indicates that it should be rounded up, confirming that the nearest whole number estimation is 2.
Remember: If the number to the right of the decimal point is 5 or greater, round up to the next whole number. If the number to the right of the decimal point is 4 or less, round down to the next whole number.
Example 3
Round 37.4 to the nearest whole number. 37.4 exists between 37 and 38. Because the tenths place is 4 or less, you know to round down. 37.4 can be rounded to 37.
Example 4
Round 18.76 to the nearest whole number. 18.76 exists between 18 and 19. Because the tenths place is 7, which is greater than 5, you know to round up. 18.76 can be rounded to 19.
Rounding to a Negative Integer
These are the rules for rounding positive numbers:
- If the number in the tenths place is 4 or less, the number in the ones place will stay the same.
- If the number in the tenths place is 5 or greater, round up.
The rules are slightly different for rounding negative numbers:
- If the number in the tenths place is 4 or less, the number in the ones place will stay the same.
- If the number in the tenths place is 5 or greater, the number will round down (further away from 0).
Remember: Once you pass zero on the number line, the numbers become negative. As you move further to the left, the numbers become more negative.
Example 5
Round -3.4 to the nearest integer. Because the tenths place is 4 or less, the ones place will stay the same. -3.4 can be rounded to -3.
If the tenths place was 5 or greater, you would round down (further away from 0) to the next whole number (in this case, -4).
Example 6
Figure 4
Figure 4 shows -1.6 on a number line. You can see that -1.6 is closer to -2, so you would round -1.6 down to -2.
Note the difference between estimation with positive integers and negative integers. With 1.6, you will go further to the right on the number line (the number would increase), because the tenths place is greater than 5. The estimation would be 2. With -1.6, you’ll do the same thing you did with 1.6, except you will go the opposite direction on the number line (to the left).
Things to Remember
- When rounding to the nearest whole number, look to the tenths place to know which way to round.
- When dealing with positive numbers, if the tenths place is 5 or greater, round up to the next number.
- If the tenths place is 4 or less, the number in the ones place stays the same.
Practice Problems
- Round 2.3 to the nearest whole number. (Solution
- Round -0.8 to the nearest integer. (Solution
- Round 72 to the nearest whole number. (Solution
- Round 2.94 to the nearest whole number. (Video Solution
- Round -24.49999 to the nearest integer. (Solution
- Round 42.0201 to the nearest whole number. (Video Solution
Need More Help?
- Study other Math Lessons in the Resource Center.
- Visit the Online Tutoring Resources in the Resource Center.
- Contact your Instructor.
- If you still need help, Schedule a Tutor.