## Rounding

For many problems numbers don't need to be exact. For example, pi () has an infinite number of digits but we usually round it off to 3.14. For many problems, this is good enough. Here are the rules for rounding numbers:

• Decide which is the last digit to keep (the "keep" digit)
For our example of the rounding of , the "keep" digit is the 4
• Leave it the same if the next digit is less than 5 (this is called rounding down)
• Increase it by 1 if the next digit is 5 or more (this is called rounding up)
• Put in zeroes for rounded off numbers past the "keep" digit if the keep digit is the 10s digit or higher.
In the case of pi (3.14) the next digit after the 4 is 1 (3.141) so we leave the 4 the same. This is rounding to the nearest hundredth because the 4 is the hundredths digit.

Here is an example, the number 4827.1836:
 Round to . . . "keep" digit ↓ rounded   number Comments Nearest thousandth 4827.1836 4827.184 3 changed to 4 because 3 was followed by 6 Nearest hundredth 4827.1836 4827.18 Nearest tenth 4827.1836 4827.2 Nearest whole number 4827.1836 4827 Nearest ten 4827.1836 4830 added a zero Nearest hundred 4827.1836 4800 added 2 zeroes Nearest thousand 4827.1836 5000 4 changed to 5 because 4 was followed by 8

Now here are some problems for you:
1. Round 56 to the nearest ten = ______

2. Round 4.159 to the nearest tenth = _____

3. Round 36.66666 to the nearest hundredth = _____

4. Round 22.7828 to the nearest whole number = ______