OPERATIONS WITH DECIMALS

Addition, Subtraction, Multiplication, Division by a whole number, and Division by a decimal

Additiion

Line up the all decimal points. Add.

2 5 . 3 9 . 7 2 0 . 6 1 8 3 5 ∙ 6 3 8

Subtraction

Line up the all decimal points. Add zeros as place holders Subtract

1 2 . 5 1 2 . 5 0- 9 . 2 6 rewritten - 9 . 2 6

3 . 2 4

Multiplication

Line up digits to be multiplied with decimals.

Multiply. Count the total number of decimal places

in the factors to find out how many decimal places the product has.

Multiplication continued

2 decimal places 1 . 2 91 decimal place x 6 . 2

2 5 87 7 4 .

3 decimal places 7 . 9 9 8

Estimate to check: 1.29 rounds down to 1. 6.2 rounds down to 6. 1 X 6 = 6This product makes sense – the product is close.

Division by a Whole Number

Divide. Put the decimal point in the quotient

directly above the decimal point in the dividend.

3 8 . 7 6

Whole Number Division continued

- 6 .

2 7 - 2 7 .

0 6 - 6

0

3 8 . 7 6

2 . 9 2

Whole Number Division continued

Estimate to check.8 . 7 6 is close to 9

9 ÷ 3 = 3

3 is close to 2 . 9 2

The quotient makes sense.

Division Using Decimals

Step 1 - move the decimal point in the divisor to the right to make a whole number.

0 . 3 4 . 8 6

Division Using Decimals continued

Step 2 – move the decimal point in the dividend the same number of places as in the divisor.

3 4 . 8 6

Step 3 Divide Put the decimal point in the quotient above

the decimal point in the dividend.

1 6 . 2 3 4 8 . 6