Part 1: Numbers

# 1.2: Rounding decimal numbers

Notes

When reporting a decimal number with lots of digits, we often round the number to make it simpler to comprehend. To round to a particular place value, we must decide whether to leave the digit in that place value at its current value (called “rounding down”) or increase the digit by 1 (called “rounding up”). To determine whether to round down or up, look at the digit for the next smaller place value. Round down if this digit is 4 or less or round up if this digit is 5 or greater. Any other digits in smaller place values can be ignored. For example, round the following numbers to the nearest thousand:

• 5,483. There are 4 hundreds, so round down to 5,000.
• 5,620. There are 6 hundreds, so round up to 6,000.
• 5,500. There are 5 hundreds, so round up to 6,000.

Round the following numbers to the nearest hundred:

• 237. There are 3 tens, so round down to 200.
• 270. There are 7 tens, so round up to 300.
• 250. There are 5 tens, so round up to 300.

Round the following numbers to the nearest ten:

• 92. There are 2 ones, so round down to 90.
• 98. There are 8 ones, so round up to 100.
• 95. There are 5 ones, so round up to 100.

Round the following numbers to the nearest whole number:

• 6.0. There are 0 tenths, so round down to 6.
• 6.7. There are 7 tenths, so round up to 7.
• 6.5. There are 5 tenths, so round up to 7.

Round the following numbers to the nearest tenth:

• 1.01. There is 1 hundredth, so round down to 1.0.
• 1.08. There are 8 hundredths, so round up to 1.1.
• 1.05. There are 5 hundredths, so round up to 1.1.

Round the following numbers to the nearest hundredth:

• 0.104. There are 4 thousandths, so round down to 0.10.
• 0.106. There are 6 thousandths, so round up to 0.11.
• 0.105. There are 5 thousandths, so round up to 0.11.

The video below shows how to round a selection of decimal numbers to various place values.

Practice Exercises

Do the following exercises to practice rounding decimal numbers. Write the number rounded to the specified place value in each box. For example, 2827.5 rounded to the nearest thousand is 3000. 