One Decimal Place Rule #1: If the last digit in 36.89 is less than 5, then remove the last digit.
One Decimal Place Rule #2: If the last digit in 36.89 is 5 or more and the second to the last digit in 36.89 is less than 9, then remove the last digit and add 1 to the second to the last digit.
One Decimal Place Rule #3: If the last digit in 36.89 is 5 or more and the second to the last digit in 36.89 is 9, then remove the last digit, make the second to last digit 0, and add 1 to the number to the left of the decimal place.
When rounding 36.89 to one decimal place we use One Decimal Place Rule #2. Therefore, the answer to "What is 36.89 rounded to 1 decimal place?" is:
36.9