Content

• To step
• Part 1 of 2: Round up to the nearest tenth
• Part 2 of 2: Special cases
• Tips

In many situations it is necessary to round numbers to one tenth so that you can work with them more easily. Once you understand tens and hundreds, the process is similar to rounding to whole numbers.

To step

Part 1 of 2: Round up to the nearest tenth

1. View rounding on a number line (optional). Let's put decimals aside for a moment, and try to round to tens first. Draw a number line from 10 to 20. The numbers on the left half of the line (such as 13 or 11) are closer to 10, so they round to 10. Rounding to decimal places can seem confusing, but it's actually the same process. You can relabel your number line to 0.10, 0.11, 0.12,…, 0.19, 0.20, so that you have a number line that you can round to one tenth.
2. Write down a number with a decimal point. It doesn't matter how many digits there are after the decimal point.
   • Example 1: Round 7.86 to the nearest tenth.
   • Example 2: Round 247.137 to the nearest tenth.
3. Find the first decimal place (tens). The first decimal is directly to the right of the decimal point. After you round to the nearest tenth, this will be the last digit of your number. Underline this figure for now.
   • Example 1: In the number 7.86, 8 is the first decimal place.
   • Example 2: In the number 247,137, 1 is the first decimal place.
4. Look at the second decimal place (hundreds). The place of the second decimal place is the digit to the right of the first decimal place after the decimal point. This number tells you whether you should round down or up.
   • Example 1: In the number 7.86, 6 is the second decimal place.
   • Example 2: In the number 247,137, 3 is the second decimal place.
   • The numbers to the right of the second decimal don't matter when you are rounding to the tenth. They represent "extra fabric" that is too small to make a difference.
5. Round up the first decimal place when the second decimal is 5 or greater than 5. Is the digit of the second decimal 5, 6, 7, 8 or 9? If so, round up by adding 1 to the first decimal place. Remove all numbers after the first decimal and you have your answer.
   • Example 1: The number 7.86 has a 6 as the second decimal place. Round off by adding 1 to the first decimal to get 7.9 and removing the numbers on the right.
6. Round down if the second decimal is 4 or less than 4. Is the digit of the second decimal 4, 3, 2, 1 or 0? If so, round down by leaving the first decimal as it is. Only delete the digits of the second decimal and to the right of it.
   • Example 2: The number 247.137 has a 3 as the second decimal place. Round down by removing everything next to the first decimal to get 247.1.

Part 2 of 2: Special cases

1. Round the first decimal down to zero. If there is a zero in the first decimal place and you round down, keep the zero in your answer. For example, 4.03 rounded to the first decimal place is 4.0. This gives people a better idea of ​​the accuracy of your number. If you only write 4, it is not wrong either, but this disguises the fact that you were working with decimals
2. Round negative numbers. Rounding off negative numbers is basically the same as rounding off positive numbers. Follow the same process and always keep the minus sign in your answer. For instance. -12.56 rounds to -12.6 and -400.333 rounds to -400.3.
   • Be careful when using the words round down and round up. If you look at a number line for negative numbers, you see that when you round -12.56 to -12.6, your number moves to the left, which you round down, even though you have increased the first decimal place by 1.
3. Round extra long numbers. Don't get confused by super long numbers. The rules remain the same. Find the first decimal and decide whether you should round up or down. After rounding, all numbers to the left of the first decimal place remain the same, and all numbers to the right of the first decimal place disappear. Here are three examples:
   • 7192403242401.29 rounds to 7192403242401.3
   • 5.0620138424107 rounds up to 5.1
   • 9000.30001 rounds up to 9000.3
4. Keep numbers without second decimal the same. Does the number end after the first decimal place, without further digits to the right? This number has already been rounded to the first decimal, so you don't have to do anything with this. That's probably a trap in your workbook.
   • For example, 1509.2 has already been rounded to the first decimal place.

Tips

• Is 5 rounded down by your teacher or in your workbook instead of up? It doesn't happen very often, but it can be. Since 5 is exactly in between two numbers, you can round up or down.