Round decimals

7th D.4 Round Decimals by Delta publications

Key Notes:

What is Rounding Decimals?

Rounding decimals means changing a decimal number to a simpler form that is close to the original value, making it easier to work with.

Why Do We Round Decimals?
  • To make numbers easier to read and use.
  • To simplify calculations.
  • To give approximate values when exact values are not necessary.
Place Value of Decimals

From left to right (after the decimal point):

  • Tenth (0.1)
  • Hundredth (0.01)
  • Thousandth (0.001)
  • Ten-thousandth (0.0001) and so on.

Example: In 45.678,

  • 6 is in the tenths place.
  • 7 is in the hundredths place.
  • 8 is in the thousandths place.
Rules for Rounding Decimals

1. Identify the place value you want to round to (tenth, hundredth, thousandth, etc.).

2. Look at the digit to the right of the place value:

  • If it is 5 or greater, add 1 to the rounding place and drop the rest.
  • If it is less than 5, keep the rounding place digit as it is and drop the rest.

3. Replace the dropped digits with zeros if needed (in whole numbers) or simply remove them (in decimals).

What is Rounding Decimals?

Example 1: Round 12.456 to the nearest tenth.

  • Tenth place = 4
  • Next digit = 5 → 5 or more → increase by 1
  • Answer = 12.5

Example 2: Round 8.734 to the nearest hundredth.

  • Hundredth place = 3
  • Next digit = 4 → less than 5 → keep as is
  • Answer = 8.73

Example 3: Round 0.999 to the nearest tenth.

  • Tenth place = 9
  • Next digit = 9 → increase by 1 (carry over)
  • Answer = 1.0
Important Notes
  • Rounding can increase or decrease the value slightly.
  • Always check the digit right after the place you are rounding to.
  • For money, we usually round to the nearest hundredth (2 decimal places).
Practice Problems

Round the following:

  1. 4.672 to the nearest tenth
  2. 19.857 to the nearest hundredth
  3. 7.999 to the nearest tenth
  4. 3.1416 to the nearest thousandth
  5. 12.345 to the nearest hundredth
Answers
  1. 4.7
  2. 19.86
  3. 8.0
  4. 3.142
  5. 12.35

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!