Adding and subtracting decimals

1
Adding and subtracting decimals
Whats the easiest way of adding and subtracting
decimals?
Use the column method!
When you use the column method you have to ensure
that you place each of the numbers in their
correct place value columns
Tens Units . (point) Tenths Hundredths
Thousandths
What you have to remember is the decimal point
appears in the answer in exactly the same place
as in the question numbers
Get into the habit of putting the first number on
the top and the second number on the bottom.
Never start changing the order.
3
0
.
8
When adding or subtracting you always start from
the right and work left.
.
1
2
0
.
9
5
0
0 . 3 8
0 . 2 1

2
Adding and subtracting decimals
Whats the easiest way of adding and subtracting
decimals?
Use the column method!
When you use the column method you have to ensure
that you place each of the numbers in their
correct place value columns
Tens Units . (point) Tenths Hundredths
Thousandths
What do we do if two numbers add up to more than
9?
Dont forget to add on the 1 that we carried on
from the last calculation. You could cross it out
so we dont count it again.
5
2
.
6
We carry the tens value on to the next column
.
5
3
1
.
1
8
3
1
9
2 . 5 6
1 . 3 5

3
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4
Adding and subtracting decimals
Whats the easiest way of adding and subtracting
decimals?
Use the column method!
When you use the column method you have to ensure
that you place each of the numbers in their
correct place value columns
Tens Units . (point) Tenths Hundredths
Thousandths
It is essential that when subtracting numbers you
do not change the order of the numbers. First
number on top, second number on bottom, or you
will get the wrong answer
What you have to remember is the decimal point
appears in the answer in exactly the same place
as in the question numbers
7
0
.
2
When adding or subtracting you always start from
the right and work left.
.
1
4
0
.
1
3
0
0 . 7 2
0 . 4 1
-
5
Adding and subtracting decimals
Whats the easiest way of adding and subtracting
decimals?
Use the column method!
When you use the column method you have to ensure
that you place each of the numbers in their
correct place value columns
Tens Units . (point) Tenths Hundredths
Thousandths
At the moment we can not do 2 5. So what do we
do?
We borrow 1 from the column to the left.
7
7
3
.
2
1
1
We borrow from the column next to it on the left
The 1 that we borrowed can then be written next
to the 2 to make 12. We can then do 12 5.
.
5
2
2
.
8
5
1
3 . 8 2
2 . 2 5
-
6
Adding and subtracting decimals
Whats the easiest way of adding and subtracting
decimals?
Use the column method!
When you use the column method you have to ensure
that you place each of the numbers in their
correct place value columns
Tens Units . (point) Tenths Hundredths
Thousandths
3
3
0
0
1
.
3
1
1
We borrow 1 from the column to the left.
We borrow 1 from the column to the left.
.
6
2
1
.
7
8
2
4 . 1 3
1 . 2 6
-
7
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