Module 5: Multiplying Decimals

1
Module 5 Multiplying Decimals
2
The key to multiplying decimals is simply knowing
your multiplication facts!
3
Step 1

• Multiply as if the factors were whole numbers
  

4
Step 1

• 8.5 x 2.5
• 85
• X25
• 4 2 5
• 1 7 0 0
• 2 1 2 5 next..

5
Step 2

• Count the total decimals moves in EACH factors
• 8.5 x 2.5 2 moves total

6
Step 1

• 8.5
• X2.5
• 4 2 5
• 1 7 0 0
• 2 1 2 5 next..

7
Step 3

• Move the TOTAL deci moves in the product

8
Step 1

• 8.5
• X2.5
• 4 2 5
• 1 7 0 0
• 2 1 .2 5

9
Try These

1) 4.8 2) 3.55 x 0.5
x .05
10
Answers

1) 4.8 48 2) 3.55 355 x 0.5
x5 x .05 x 5 2.40
0.1775 2 moves in
product 4 moves in product
11
Lets practicewrite each problem
verticallyremember to move the total deci moves
for each FACTOR in your PRODUCT
12
34.9 X 0.15

• Basically its 349 x 15
• Then deci in product 3 times

13
34.9 X 0.15

• ANSWER
• 5.235

14
12.45 x 1.7

• 1245 x 17 21165 then move deci 3 times from the
  left in your product
• 21.165

15
12.45 x 1.7

• Answer
• 21.165

16

• 0.45 x 1.90
• Count the total deci moves. Just multiply 45x19
  then move deci moves in the product

17
0.45 x 1.90

• Answer
• 0.855

18
3.05 x 1.65

• Solve 305 x 165
• Then move total deci moves in the product

19
3.05 x 1.65

• Answer
• 5.0325

20
Try These on your own

• A) 3.7 x 0.45
• B) 98.3 x 1.7
• C) 4.5 x 0.84
• D) 89.5 x 4.9

21
Answers

• A) 3.7 x 0.45 1.665
• B) 98.3 x 1.7 167.11
• C) 4.5 x 0.84 3.78
• D) 89.5 x 4.9 438.55