Rules of Rounding

Rules for Rounding

    Introduction

There are many instances when it is necessary or helpful to round a decimal value to a value that doesn’t include the quantity following the decimal point or to a value that contains fewer decimal places. For example, if you want to know the average number of items that were requisitioned over a given period of time, you would probably want to round your answer since you can’t requisition only part of an item.

Sometimes, when you want a certain amount of precision, you may want to round to a particular decimal place, such as tenths, hundredths, or thousandths. Other times, when you only want a general estimation of a value, you may want to round to the nearest whole number, or even to the closest ten, hundred, thousand, etc.

The Professor Says:
Here are the basic steps for rounding:

Step 1.
Identify the number in the position you are rounding to.
Then look at the number to the right of that number.

Step 2.
Round the number following these rules:

If the number to the right is 5 or greater, increase the
number in the rounding position by 1 (round up).

If the number to the right is less than 5, leave the
number in the rounding position alone (round down).

Step 3.
Then complete the rounding as follows:

If you are rounding to a decimal place, drop all
numbers to the right of the number in the rounding
position.

If you are rounding to a whole number, replace all
numbers between the rounding position and the
decimal place with zeroes, and drop all decimal places.

    Examples

Round 14,549.436 to the nearest hundredth.

Rounding to the nearest hundredth means rounding to two decimal places.

              Hundredths place is rounding position
14,549.436
                Look at this number—round up
Ans. 14,549.44


Round 14,549.436 to the nearest tenth.

Rounding to the nearest tenth means rounding to one decimal place.

            Tenths place is rounding position
14,549.436
              Look at this number—round down

Ans. 14,549.4


Round 14,549.436 to the nearest whole number.

Rounding to the nearest whole number means rounding to the ones place.

         Ones place is rounding position
14,549.436
            Look at this number—round down

Ans. 14,549


Round 14,549.436 to the nearest ten.

       Tens place is rounding position
14,549.436
         Look at this number—round up

Ans. 14,550

Round 14,549.436 to the nearest hundred.

    Hundreds place is rounding position
14,549.436
       Look at this number—round down

Ans. 14,500

Round 14,549.436 to the nearest thousand.

Thousands place is rounding position
14,549.436
Look at this number—round up

Ans. 15,000

The Professor Says:

Be careful. Do not do chain rounding.

    Example

Round 436.449 to the nearest whole number.

Chain rounding would round 436.449 to 436.45 and then to 436.5 and then to 437. That is not correct. Instead, round only based on the number closest to the number you want to round to. In this case, the first 4 after the decimal point is the key; therefore, the answer is 436.

Practice