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+ - x / DECIMALS REVIEW
Contributed by: Johnson
(Original author: Cason)

When adding or subtracting, line up the decimals. 

Watch for numbers without decimals.  THEY ARE

WHOLE NUMBERS.  Their decimals are at the end like

a period at the end of a sentence.

3 + 5.9 + 2.3 would be as follows...

Put a decimal

behind

the 3.

11.2
1

3.0

5.9

2.3

9 + 3 = 12

Carry the one.

4.6 + 5 + 9.7 becomes...

+

4 . 6

 

 

9 . 7

.
54.93 + 4.98 =
6.3 + 7 + 5.9 =

When subtracting decimals, still line up the decimals

making sure to put decimals behind any whole numbers.

If the top digit is smaller than the bottom digit in a

place value, you must rename.

   5.0

- 1.2
3.8

4

10

  4.0

-2.6

 

  8.4

-2.8

 

  6 - 3.7 =

100 - 4.5 =

When multiplying, we do not need to  line up decimals.

Multiply as if the decimals are not there.  Then count

how many digits are behind the decimals for each

factor.  Make sure the answer has the same number

behind it.  3.4 x .04 is as follows.

 0.136

     3.4

x 0.04

three place values
one place value
two place value
+

Fill in your work.

   3.25

x   0.4

 .

In 4.23 x 3.7 how many places are behind the decimal

in your answer?

place values left
Multiply.  3.2 x .7

Fill in all  9

missing digits.

   3 . 4 2

   x   1.4

1 3      8

 

   .7

      4.6 3

   x 1 3.4

Needs to move                          Doesn't need to move.

Since we can't divide by a decimal, if the divisor is a

decimal, move the decimal to the end to make it a

whole number.  THEN, MOVE THE SAME NUMBER OF

PLACES VALUES IN THE DIVIDEND.  If a number has no

visible decimal, its a whole number.  Its decimal is at

the end.

1.6   8
.

5.

.
.
16    .8

.05

0.057

0.57

5.7

Select the answer with the decimal in the correct place.

23

1.311

57

9.135 ÷ 4.5 =

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