Adding and
Subtracting Decimals
Essential Question:
• How do I add and subtract decimals?
• Always line up decimals
• Add and subtract like you always do
• Bring decimal straight down in your
answers
Adding
Examples:
4.55 + 11.3
Put the first number on
the top of the second
number and line up the
decimals.
You can
add a zero
to help
4.55
keep
+ 11.30
everything
lined up
15.85
When adding
or subtracting
you always
start from the
right and work
left.
6.44 + 16
When there is
not a decimal
put one
behind the
number.
Line up
the
decimal
6.44
+ 16.0
22.44
Add a
zero to
line up
everythin
g
-8.33 + -10.972
Line up
the decimal
-8.330
+ -10.972
-19.302
Add a
zero to
line up
everythin
g
Same signs
Add – keep
the sign
Subtracting
Examples:
5.34 -2.08
Put the first number on
the top of the second
number and line up the
decimals.
5.34
-2.08
3.26
Different signs
Take difference
-38.59 – (-7.81)
+
Line up
the decimal
-38.59
+ 7.81
-30.78
Subtract to
add when
negatives are
used.
Different signs
take
difference
28 – 15.911
When there
is
not a decimal
put one
behind the
number.
7 99
28. 000
-15.911
1 2.0 8 9
Add zeros to
line up
everything,
then
subtract
Magic Square
0.5
7
4.625
8.75
The sum of each
row, column,
and diagonal
must be the
same.
6.375
0.5
7
5.25
4.625
4
2.25
8.75
2.875
Sums to
13.875