Brain Buster Rounding
Rounding off is kind of like estimating.
The rules for rounding decimals are the same as whole numbers but we need to locate the correct decimal place.
Questions will usually be asked in one of two ways: To the nearest tenth, hundredth, or thousandth, or to one, two, or three decimal places “One decimal place" is the same as "the nearest tenth”. “Two decimal places” is the same as “the nearest hundredth”. “Three decimal places” is the same as “the nearest thousandth.”
For example in the number 5.123
The 1 is in the tenths place and is the first decimal place
The 2 is in the hundredths place and is the second decimal place
The 3 is in the thousandths place and is the third decimal place.
Once we have located the correct digit we follow the same rule as for whole numbers.
1. Highlight the digit that may change.
2. Underline the digit on the right.
3. Round the highlighted digit
a. If the underlined digit is 5 or more the highlighted digit is increased by 1.
b. If the underlined digit is 4 or less the highlighted digit stays the same.
4. All the digits to the right of the highlighted digit are changed to zeros.
Round 5.123 to 2 decimal places.
Step 1: Find the place value we are rounding to.
We are rounding to 2 decimal places, so that is the 2.
Step 2: Look at the number to the right of the one we’re rounding.
Step 3: Round the number.
The number next to the 2 is a 3, which means the 2 stays the same.
Step 4: For a whole number we set the trailing digits to 0's but in decimals they have no meaning so we can just drop them.
The answer is 5.120 which can be written as 5.12