1. Multiply Decimals

2. To multiply decimals:
Write the problem vertically, lining up the numbers as if they are whole numbers. Do NOT line up decimal points.
4.8 x .31
4.8
x .3 1

3. 2. Multiply as if they are whole numbers.
4.8 x .31
4.8
x .3 1
4 8

4. You have 2 decimal places
3. Count the total number of decimal places in the factors.
4.8
x .3 1
4 8
Final Answer:
You have 1 decimal place
in the first factor.
You have 2 decimal places
in the second factor.
For a total of 3 decimal
places.

5. Another Example:
Write the problem vertically, lining up the numbers as if they are whole numbers. Do NOT line up decimal points.
.123 x .43
.123
x .43

6. 2. Multiply as if they are whole numbers.
.123 x .43
.123
x .43
369
5289

7. You have 3 decimal places
3. Count the total number of decimal places in the factors.
.123 x .43
.123
x .43
369
5289
You have 3 decimal places
in the first factor.
You have 2 decimal place
in the second factor.
For a total of 5 decimal
places.

8. .123
x .43
369
5289
What do I do now? I have an “empty space”?
Add a zero.
Final Answer:

9. Your Turn:
a) 23.1 x 4.2
=97.02
b) 1.52 x 3
=4.56