1. Rules for Adding, Subtracting, Multiplying, Dividing, and Rounding
Decimals
Rules for Adding, Subtracting, Multiplying, Dividing, and Rounding

2. Adding Decimal Numbers
Adding decimals is very much like adding whole numbers.
The most important thing to remember when adding decimals is to line up all the decimal points in a column!
You can put in 0’s as place holders if you would like to help keep the columns straight, but it’s not necessary.
Place the decimal point in the answer directly below the decimal points in the terms.

3. Adding Decimal Numbers

4. Subtracting Decimal Numbers
Put the numbers in a vertical column lining up the decimal points.
You must put in 0’s as place holders to help keep the columns straight, but also so you’ll know if you need to borrow.
Subtract each column, starting on the right and working left. If the top number is smaller than the bottom number, borrow from the top number at the left.
Place the decimal point in the answer directly below the decimal points in the terms.

5. Subtracting Decimal Numbers

6. Multiplying Decimal Numbers
Put the numbers so that the last digits line up, without trying to line up the decimal points.
Do NOT put in 0’s as place holders.
Multiply as if the numbers were whole numbers.
Determine the TOTAL number of digits to the right of the decimal points in the numbers.
Place the decimal point in the answer so the number of digits to the right of the decimal point is the same as the TOTAL number of digits above.

7. Multiplying Decimal Numbers

8. Dividing Decimal Numbers
Multiply both the dividend and divisor by a power of 10 that will make the divisor (number you are dividing by) a whole number (or just move the required number of decimal places, filling in 0’s where needed).
Divide as if working with whole numbers.
Place the decimal point in the answer directly above the decimal point in the dividend.

9. Dividing Decimal Numbers

10. Rounding Decimal Numbers
Identify the number in the problem to the right of the positional value to which the number is to be rounded
For example, if you wish to round to tenths, you identify the number in the hundredths position.
If the number you identified above is greater than or equal to 5, the number in the preceding position is increased by 1 unit and all numbers to the right are eliminated.
If the number you identified above is less than 5, the number in the preceding position stays as it is and all numbers to the right are eliminated

11. Rounding Decimal Numbers