1. Medical Math Lesson
Adding and
Subtracting Decimals
September - 2012

2. Essential Question:
• How do I add and subtract decimals?
It is very important that you:
1.Always line up decimals
2.Add and subtract like you always do
3.Bring decimal straight down in your
answers

3. Adding
Examples:
4.55 + 11.3
Put the first number on
the top of the second
number and line up the You can
decimals. add a zero
to help
keep
4.55 everything
lined up
+ 11.3 0 When adding
or subtracting
1 5. 8 5 you always
start from the
right and work
left.

4. 6.44 + 16
When there is
not a decimal
put one
behind the
6+6=12 number.
Write down
the 2 and Add a zero
carry the 1. to line up
Line up everything
1 6.44
the
decimal + 16. 0 0
22 . 4 4

5. 8.33 + 10.972
Annex (add) a
1 1 zero which acts
as a decimal
8.330 place holder and
Set up vertically and
helps lining up
line up + 10.972 the numbers.
the decimals
1 9 .3 0 2
Adding a zero is
also called
annexing a zero.
It doesn’t change
the value of the
number.

6. Subtracting
Examples:
5.34 -2.08
Put the larger number on
the top of the smaller
number and line up the
Don’t forget you may
decimals. Need to borrow
from the left
to get the
2 job done’
/4
5.3 1
-2.0 8
14-8=6
3. 2 6
2-0=2
5-2=3

7. 28 – 15.911 Stack them
and line up
the
decimal
When there is points.
not a decimal,
as in the 28, Add zeros to
put one line up
behind the 7 99 everything,
number. then
28.0001
subtract
-15.911
1 2.08 9
Start borrowing
from the left.
Start with the
first number
smaller than the
number under it.

8. Magic Square
0.5 7
4.625
8.75
The sum of each 6.375 0.5 7
row, column,
and diagonal 5.25 4.625 4
must be the
2.25 8.75 2.875
same.
Sums to
13.875

9. Assignment: Problems 1-16 to be completed
without a calculator. Remember to show your
work for any credit. Turn into your instructor.
Edmodo quiz on addition and subtraction of
decimal values.