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:
 Round 56 to the nearest ten = ______
 Round 4.159 to the nearest tenth = _____
 Round 36.66666 to the nearest hundredth = _____
 Round 22.7828 to the nearest whole number = ______
