4.082 rounded to the nearest hundredth

The hundredths digit is two places to the right of the decimal point. In this case, the hundredths place has an eight in it. To round, look at the digit to its immediate right, and if it is less than 5, round down and keep it as eight. You drop every number to the right of the eight after that. If it is 5 or greater than 5, then round up. 8 becomes 9, and all digits behind the 9 in that case would be dropped. 
In this case, the thousandths digit is less than 5, because 2 < 5, so we round down, and the number becomes 4.08. 
Hope that helped you.

Use a calculator basically