Round decimals

Key Notes:

What is Rounding?

  • Rounding is a way to simplify numbers by making them easier to work with.
  • It involves changing a number to a nearby value that is a multiple of 10, 100, 1000, etc.
  • We round decimals to a specific place value, such as the nearest whole number, tenth, hundredth, or thousandth.

Rules for Rounding Decimals:

  1. Identify the place value you want to round to.
  2. Look at the digit to the right of that place value.
  3. If the digit is 5 or greater, round up.
  4. If the digit is less than 5, round down.

Examples:

  • Rounding to the Nearest Whole Number:
    • 3.7 rounds to 4
    • 5.2 rounds to 5
  • Rounding to the Nearest Tenth:
    • 2.34 rounds to 2.3
    • 8.76 rounds to 8.8
  • Rounding to the Nearest Hundredth:
    • 1.235 rounds to 1.24
    • 4.567 rounds to 4.57

Real-World Applications:

  • Money: Rounding prices to the nearest dollar or cent.
  • Measurements: Rounding measurements in science and engineering.
  • Statistics: Rounding averages and other statistical values.

Learn with an example

What is 52.8 rounded to the nearest whole number?

First, find the digit in the ones place. This is the place you want to round:

52.8

Now look one place to the right:

52.8

8 is greater than 5, so you will round up. Remove all the digits to the right of the ones place:

52.8 → 52

Now add 1 to the number:

52 → 53

What is 31.8 rounded to the nearest whole number?

First, find the digit in the ones place. This is the place you want to round:

31.8

Now look one place to the right:

31.8

8 is greater than 5, so you will round up. Remove all the digits to the right of the ones place:

31.8 → 31

Now add 1 to the number:

31 → 32

What is 93.3 rounded to the nearest whole number?

First, find the digit in the ones place. This is the place you want to round:

93.3

Now look one place to the right:

93.3

3 is less than 5, so you will round down. Remove all the digits to the right of the ones place:

93.3 → 93

What is 8.2 rounded to the nearest whole number?

First, find the digit in the ones place. This is the place you want to round:

8.2

Now look one place to the right:

8.2

2 is less than 5, so you will round down. Remove all the digits to the right of the ones place:

8.2 → 8

What is 2.5 rounded to the nearest whole number?

First, find the digit in the ones place. This is the place you want to round:

2.5

Now look one place to the right:

2.5

5 is equal to 5, so you will round up. Remove all the digits to the right of the ones place:

2.5 → 2

Now add 1 to the number:

2 → 3

Try some practice problems!