1. This document provides a lesson on adding and subtracting decimals. It emphasizes lining up the decimals and notes that adding and subtracting decimals follows the same process as whole numbers. 2. Examples are provided that demonstrate adding decimals by lining them up under each other with the decimals in the same column before adding. Adding zeros as placeholders is explained to help line up the decimals. 3. Subtracting decimals is demonstrated with examples of lining up the numbers with the larger number on top and subtracting left to right, borrowing as needed from the left.

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.