1. Preview
Warm Up
California Standards
Lesson Presentation

2. Warm Up
Write each number as an improper fraction. 1 7 3 7 15 8 2 17 5 1. 2 2. 1 3. 3 3 8 5 2 20 3 3 43 8 4. 6 5. 5 3 8

3. NS1.2 Add, subtract, multiply, and divide rational numbers (integers, fractions, and terminating decimals) and take positive rational numbers to whole-number powers.
California
Standards

5. Additional Example 1A: Multiplying Fractions
Multiply. Write the answer in simplest form.
1 8
6 7 =
1(6) 8(7)
Multiply numerators.
Multiply denominators. 3 4
1(6) 8(7) =
Look for common factors: 2.
3 28 =
Simplify.

6. Additional Example 1B: Multiplying Fractions
Multiply. Write the answer in simplest form.
2 3
1 2 – 4
1 2
2 3 – 4
9 2 =
Write 4 as an improper fraction. 12 =
–2(9) 3(2)
Multiply numerators.
Multiply denominators. 1 –1 3 1
–2(9) 3(2) =
Look for common factors: 2, 3. –3 =
Simplify.

7. 3 5 5 8 3(5) 5(8) = 3(5) 5(8) = 3 8 = Multiply numerators.
Check It Out! Example 1A
Multiply. Write the answer in simplest form.
3 5
5 8 =
3(5) 5(8)
Multiply numerators.
Multiply denominators. 1
3(5) 5(8) =
Look for common factors: 5.
3 8 =
Simplify.

8. 7 8 4 7 – = –7(4) 8(7) –1 –7(4) 8(7) = 1 2 = – Multiply numerators.
Check It Out! Example 1B
Multiply. Write the answer in simplest form.
7 8
4 7 – =
–7(4) 8(7)
Multiply numerators.
Multiply denominators. 1 –1 1 2
–7(4) 8(7) =
Look for common factors: 4, 7.
1 2
= –
Simplify.

9. To multiply a fraction by an integer, first write the integer as a fraction with a denominator of 1. Then multiply as you would with two fractions.

10. Additional Example 2: Application
Joy completes of her painting each day.
How much of her painting does she complete in a 7 day week?
1 20
1 20
1 20 71
(7) =
Write the integer 7 as a fraction.
1 • 7 20 • 1
Multiply numerators and denominators. =
7 20 =
Joy completes of her painting in a 7-day week.
7 20

11. Check It Out! Example 2
1 7
Mark runs mile each day. What is the total
distance Mark runs in 5 days?
1 7
1 7 51
(5) =
Write the integer 5 as a fraction.
1 • 5 I7 • 1
Multiply numerators and denominators. =
5 7 =
Mark runs mile in 5 days.
5 7

12. To multiply decimals, first multiply as you would with integers
To multiply decimals, first multiply as you would with integers. The number of decimal places in the product is equal to the sum of the number of decimal places in the factors.

13. Additional Example 3: Multiplying Decimals2
0 decimal places
 –0.51
2 decimal places
–1.02
0 + 2 = 2 decimal places.
B. (–0.4)(–3.75)
–3.75
2 decimal places
 -0.4
1 decimal place
1.500
2 + 1 = 3 decimal places
or 1.5

14. Check It Out! Example 3
Multiply.
A. 3.1(0.28)
3.1
1 decimal place 
2 decimal places
0.868
1 + 2 = 3 decimal places
B. (–0.4)(–2.53)
–0.4
1 decimal place
 –2.53
2 decimal places
1.012
1 + 2 = 3 decimal places

15. – – Lesson Quiz Multiply. 1 7 2 7 1. 1 9 2 3 5 8 5 12 2. 3. –0.47(2.2)
–1.034
1 2 45
4. Evaluate 2 (x) for x = . 2
8 9
Edgar runs mile each day. What is the total distance that Edgar runs in a 7-day week? 5.
6 miles
2 9