1. 3-6 Multiplying Decimals Warm Up Problem of the Day
Course 1
Warm Up
Problem of the Day
Lesson Presentation

2. 3-6 Multiplying Decimals Warm Up Multiply. 1. 87  320 27,840
Course 1
3-6
Multiplying Decimals
Warm Up
Multiply.
1. 87  320
27,840
 800
754,400
3. 3,806  10
38,060
4. 1,207  100
120,700
5. 72  196
14,112
 523
62,760

3. 3-6 Multiplying Decimals Problem of the Day
Course 1
3-6
Multiplying Decimals
Problem of the Day
Carmen and Rita sold homemade oatmeal cookies. After 8 days, they had sales totaling $70. Each day, their sales were $0.50 higher than the previous day. What were their sales on the first day?
$7.00

4. 3-6 Multiplying Decimals
Course 1
3-6
Multiplying Decimals
Learn to multiply decimals by whole numbers and by decimals.

5. Additional Example 1: Science Application
Course 1
3-6
Multiplying Decimals
Additional Example 1: Science Application
Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 4 lb dumbbell weigh on the Moon?
4  0.17
You can think of multiplication by a whole number as a repeated addition.
0.17
0.17
0.17
+ _____
0.17
0.68

6. Additional Example 1 Continued
Course 1
3-6
Multiplying Decimals
Additional Example 1 Continued
Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 4 lb dumbbell weigh on the Moon?
You can also multiply as you would with whole numbers. Place the decimal point by adding the number of decimal places in the numbers multiplied.
0.17
2 decimal places 4
+ 0 decimal places
 _____
2 decimal places
0.68
A 4 lb dumbbell on Earth weighs 0.68 lb on the Moon.

7. 3-6 Multiplying Decimals Try This: Example 1
Course 1
3-6
Multiplying Decimals
Try This: Example 1
Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 7 lb dumbbell weigh on the Moon?
7  0.17
You can think of multiplication by a whole number as a repeated addition.
0.17
0.17
0.17
0.17
0.17
0.17
0.17
+ _____
1.19

8. Try This: Example 1 Continued
Course 1
3-6
Multiplying Decimals
Try This: Example 1 Continued
Something that weighs 1 lb on Earth weighs 0.17 lb on the Moon. How much would a 7 lb dumbbell weigh on the Moon?
You can also multiply as you would with whole numbers. Place the decimal point by adding the number of decimal places in the numbers multiplied.
0.17
2 decimal places
 _____ 7
+ 0 decimal places
2 decimal places
1.19
A 7 lb dumbbell on Earth weighs 1.19 lb on the Moon.

9. Additional Example 2A: Multiplying a Decimal by a Decimal
Course 1
3-6
Multiplying Decimals
Additional Example 2A: Multiplying a Decimal by a Decimal
Find the product.
A. 0.3  0.4
Multiply. Then place the decimal point.
1 decimal place
0.3 
+ 1 decimal place
0.4
2 decimal places
0.12

10. Additional Example 2B: Multiplying a Decimal by a Decimal
Course 1
3-6
Multiplying Decimals
Additional Example 2B: Multiplying a Decimal by a Decimal
B  0.8
Estimate the product. 0.8 is close to 1.
0.07  1 = 0.07
Multiply. Then place the decimal point.
2 decimal places
0.07
+ 1 decimal place 
0.8
3 decimal places; use a placeholder zero
0.056
0.056 is close to the estimate of The answer is reasonable.

11. Additional Example 2C: Multiplying a Decimal by a Decimal
Course 1
3-6
Multiplying Decimals
Additional Example 2C: Multiplying a Decimal by a Decimal
C  2.5
Estimate the product. Round each factor to the nearest whole number.
1  3 = 3
Multiply. Then place the decimal point.
1.34 
2.5
2 decimal places
670
+ 1 decimal place
2680
3 decimal places
3.350
3.350 is close to the estimate of 3. The answer is reasonable.

12. 3-6 Multiplying Decimals  Try This: Example 2A Find each product.
Course 1
3-6
Multiplying Decimals
Try This: Example 2A
Find each product.
A. 0.5  0.2
Multiply. Then place the decimal point.
1 decimal place
0.5 
+ 1 decimal place
0.2
2 decimal places
0.10

13. 3-6 Multiplying Decimals  Try This: Example 2B B. 0.03  0.9
Course 1
3-6
Multiplying Decimals
Try This: Example 2B
B  0.9
Estimate the product. 0.9 is close to 1.
0.03  1 = 0.03
Multiply. Then place the decimal point.
2 decimal places
0.03
+ 1 decimal place 
0.9
3 decimal places; use a placeholder zero
0.027
0.027 is close to the estimate of The answer is reasonable.

14. 3-6 Multiplying Decimals  Try This: Example 2C C. 3.80  3.3
Course 1
3-6
Multiplying Decimals
Try This: Example 2C
C  3.3
Estimate the product. Round each factor to the nearest whole number.
4  3 = 12
Multiply. Then place the decimal point.
3.80 
3.3
2 decimal places
1140
+ 1 decimal places
11400
3 decimal places
12.540
12.54 is close to the estimate of 12. The answer is reasonable.

15. Additional Example 3A: Evaluating Decimal Expressions
Course 1
3-6
Multiplying Decimals
Additional Example 3A: Evaluating Decimal Expressions
Evaluate 5x for each value of x.
A. x = 3.062
Substitute for x.
5x = 5(3.062)
3 decimal places
3.062  5
+ 0 decimal places
15.310
3 decimal places
These notations all mean multiply 3 times x.
3 • x 3x 3(x)
Remember!

16. Additional Example 3B: Evaluating Decimal Expressions
Course 1
3-6
Multiplying Decimals
Additional Example 3B: Evaluating Decimal Expressions
B. x = 4.79
Substitute 4.79 for x.
5x = 5(4.79)
2 decimal places
4.79
+ 0 decimal places  5
23.95
2 decimal places

17. 3-6 Multiplying Decimals  Try This: Example 3A
Course 1
3-6
Multiplying Decimals
Try This: Example 3A
Evaluate 5x for each value of x.
A. x = 2.012
Substitute for x.
5x = 5(2.012)
3 decimal places
2.012
+ 0 decimal places  5
10.060
3 decimal places

18. 3-6 Multiplying Decimals  Try This: Example 3B B. x = 6.22
Course 1
3-6
Multiplying Decimals
Try This: Example 3B
B. x = 6.22
Substitute 6.22 for x.
5x = 5(6.22)
2 decimal places
6.22  5
+ 0 decimal places
31.10
2 decimal places

19. Insert Lesson Title Here
Course 1
3-6
Multiplying Decimals
Insert Lesson Title Here
Lesson Quiz
Find each product.
 0.07
Evaluate 8x for each value of x.
 0.07
0.056
3. x = x = 0.804
21.64
6.432
5. “Pick your own” peaches sell for $0.95 per pound. You picked 92 pounds of peaches. How much were you charged?
$87.40