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Decimal Operations Guide

To add or subtract decimals, line up the decimal points and fill in zeros as needed. Then perform the operation as if they were whole numbers and place the decimal point in the sum or difference accordingly. To multiply decimals, multiply as if they were whole numbers and the number of decimal places in the product equals the sum of decimal places in the factors. To divide decimals, move the decimal points to make the divisor a whole number, place the decimal point in the quotient over the dividend's decimal point, and divide as whole numbers.

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91 views5 pages

Decimal Operations Guide

To add or subtract decimals, line up the decimal points and fill in zeros as needed. Then perform the operation as if they were whole numbers and place the decimal point in the sum or difference accordingly. To multiply decimals, multiply as if they were whole numbers and the number of decimal places in the product equals the sum of decimal places in the factors. To divide decimals, move the decimal points to make the divisor a whole number, place the decimal point in the quotient over the dividend's decimal point, and divide as whole numbers.

Uploaded by

Edzel Joson
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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OPERATIONS WITH DECIMALS

TO ADD OR SUBTRACT DECIMALS:

1) Line up the decimal points vertically. Fill in any 0's where necessary.

2) Add or subtract the numbers as if they were whole numbers.

3) Place the decimal point in the sum or difference so that it lines up vertically with the numbers being added or
subtracted.

EXAMPLE 1: Add 0.56 + 9 + 6.287

To add decimals, line up the decimal points vertically and fill in 0's as shown:

0.560
9.000
+ 6.287

15.847 ← Place the decimal point in the sum so that it lines up vertically.

EXAMPLE 2: Subtract 6 – 1.859

To subtract decimals, line up the decimal points vertically and add 0's where shown. Remember to borrow
when necessary.

5 9 9 10
6 .0 0 0
1.8 5 9
Add to check!
4 .141

EXAMPLE 3: Subtract 3.742 – 10.638

If the decimals have opposite signs, place the larger decimal on top, line up the decimal points, subtract
the numbers, and carry down the sign, as shown:

– 10.638
3.742
– 6.896

PBCC 1 SLC Lake Worth Math Lab


TO MULTIPLY DECIMALS:

1) Multiply the decimals as if the decimals were whole numbers.

2) To place the decimal point, count the number of decimal places in each factor.

3) The number of decimal places in the product is the sum of the number of decimal places in each factor.

EXAMPLE 4: Multiply 3.48 x 12.7

Multiply the decimals as if they were whole numbers. Then count the number of decimal places in each
factor. Since the total number of decimal places in each factor is 3, the product must have 3 decimal places.
(Note: the decimal points are not lined up when we multiply decimals.)

3.48
 2 decimal places
x 12.7
 1 decimal place
2436
6960
34800
44.196.
 3 decimal places

3.48 x 12.7 = 44.196

PBCC 2 SLC Lake Worth Math Lab


TO DIVIDE DECIMALS:

1) When the divisor is a whole number, place the decimal point in the quotient directly over the
decimal point in the dividend. Then divide the numbers as if they were whole numbers.

EXAMPLE 6: Divide 0.54  12

Because the divisor is a whole number, the decimal point in the dividend does not move. Place the decimal
point in the quotient directly above the decimal point in the dividend. Then carry out the division until it
terminates, adding any 0's to the dividend where necessary:

Place the decimal point Quotient

0. 045
Divisor 12 0. Dividend
540
 48
60
60
0

2) When the divisor is a decimal, move the decimal point in the divisor as many places as necessary to
make it a whole number. Move the decimal point in the dividend the same number of places to the right.
Place the decimal point in the quotient directly over the decimal point in the dividend. Then divide the
numbers as if they were whole numbers.

EXAMPLE 7: Divide 2.176  0.34

Move the decimal point in the divisor 2 places to get a whole number. Then move the decimal point in the
dividend the same number of places to the right. Place the decimal point in the quotient directly over the
moved decimal point in the dividend, as shown.

6.4
0.34 . 2.17 .6
 20 4
136
 136
0

PBCC 3 SLC Lake Worth Math Lab


EXAMPLE 8: Divide 63  2.8

Move the decimal point in the divisor 1 place to get a whole number. Add a decimal point and a zero to the
dividend. Then move the decimal point in the dividend 1 place and carry out the division.

22.5
2.8 63 2 . 8 . 63 .0 .  28 630.0
56
70
56
140
140
0

PBCC 4 SLC Lake Worth Math Lab


PBCC 5 SLC Lake Worth Math Lab

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