1. Course 1 5-7 Multiplying Fractions 5-7 Multiplying Fractions Course 1 Warm Up Warm Up Problem of the Day Problem of the Day Lesson Presentation Lesson Presentation

2. Course 1 5-7 Multiplying Fractions Warm Up 1. What is of 12? 2. What is of 100? 3. What is of 120? 4. What is of 100? 5. What is of 480? 6 50 60 1 2 __ 1 2 1 2 1 4 1 4 25 120

3. Course 1 5-7 Multiplying Fractions Problem of the Day Your favorite uncle left one-fifth of his estate to each of his three children and the rest to his favorite charity. If his estate was worth $105,000, how much was given to charity? $42,000

4. Course 1 5-7 Multiplying Fractions Learn to multiply fractions.

5. Course 1 5-7 Multiplying Fractions On average, people spend of their lives asleep. About of the time they sleep, they dream. What fraction of a lifetime does a person typically spend dreaming? 1 3 __ 1 3 1 4 1 4 1 4 1 3 1 4 1 3 = 1 12 __ One way to find of is to make a model. Find of.

6. Course 1 5-7 Multiplying Fractions You can also multiply fractions without making a model. 1 4 __ 1 3 1 1 4 3 _____ 1 12 __ = = Multiply the numerators. Multiply the denominators. A person typically spends of his or her lifetime dreaming. 1 12 __ The answer is in simplest form.

7. Course 1 5-7 Multiplying Fractions Additional Example 1A: Multiplying Fractions Multiply. Write each answer in simplest form. 1 4 __ 2 5 _____ = = Multiply numerators. Multiply denominators. 2 20 __ 1 2 4 5 1 4 __ 2 5 __ The GCF of 2 and 20 is 2. The answer is in simplest form. = 1 10 __

8. Course 1 5-7 Multiplying Fractions Additional Example 1B: Multiplying Fractions Multiply. Write each answer in simplest form. 5 7 __ 4 15 __ _____ = = Use the GCF to simplify the fractions before multiplying. The greatest common factor of 5 and 15 is 5. 4 21 __ 1 4 7 3 5 7 __ 4 15 __ Multiply numerators. Multiply denominators. The answer is in simplest form. 1 7 __ 4 3 __ 1 3 =

9. Course 1 5-7 Multiplying Fractions Additional Example 1C: Multiplying Fractions Multiply. Write each answer in simplest form. 4 9 __ 6 10 __ ______ = = Multiply numerators. Multiply denominators. 24 90 __ 4 6 9 10 4 9 __ 6 10 __ The GCF of 24 and 90 is 6. The answer is in simplest form. = 4 15 __

10. Course 1 5-7 Multiplying Fractions Check It Out: Example 1A Multiply. Write each answer in simplest form. 1 2 __ 3 6 _____ = = Multiply numerators. Multiply denominators. 3 12 __ 1 3 2 6 1 2 __ 3 6 __ The GCF of 3 and 12 is 3. The answer is in simplest form. = 1 4 __

11. Course 1 5-7 Multiplying Fractions Check It Out: Example 1B Multiply. Write each answer in simplest form. 3 7 __ 5 9 _____ = = Use the GCF to simplify the fractions before multiplying. The greatest common factor of 3 and 9 is 3. 5 21 __ 1 5 7 3 3 7 __ 5 9 __ Multiply numerators. Multiply denominators. The answer is in simplest form. 1 7 __ 5 3 __ 1 3 =

12. Course 1 5-7 Multiplying Fractions Check It Out: Example 1C Multiply. Write each answer in simplest form. 3 7 __ 5 15 __ ______ = = Multiply numerators. Multiply denominators. 15 105 ____ 3 5 7 15 3 7 __ 5 15 __ The GCF of 15 and 105 is 15. The answer is in simplest form. = 1 7 __

13. Course 1 5-7 Multiplying Fractions Additional Example 2A: Evaluating Fraction Expressions 2 5 __ 1 3 b 2 5 2 5 1 3 _____ 1 2 3 5 2 15 __ Substitute for b. 1 3 __ Multiply. The answer is in simplest form. b = Evaluate the expression b for each value of b. Write each answer in simplest form.

14. Course 1 5-7 Multiplying Fractions You can look for a common factor in a numerator and a denominator to determine whether you can simplify before multiplying. Helpful Hint

15. Course 1 5-7 Multiplying Fractions Additional Example 2B: Evaluating Fraction Expressions b = 3 8 __ b 2 5 2 5 3 8 _____ 3 1 4 5 3 20 __ Substitute for b. 3 8 __ Use the GCF to simplify. The answer is in simplest form. 1 4 2 5 __ 3 8 Multiply.

16. Course 1 5-7 Multiplying Fractions Additional Example 2C: Evaluating Fraction Expressions b = 5 7 __ b 2 5 2 5 5 7 _____ 5 2 7 5 10 35 __ Substitute for b. 5 7 __ Multiply. The GCF of 10 and 35 is 5. The answer is in simplest form. 2 7 __

17. Course 1 5-7 Multiplying Fractions Check It Out: Example 2A Evaluate the expression c for each value of c. Write each answer in simplest form. c = 1 4 __ 1 7 c 1 4 1 4 1 7 _____ 1 7 4 1 28 __ Substitute for c. 1 7 __ Multiply. The answer is in simplest form.

18. Course 1 5-7 Multiplying Fractions Check It Out: Example 2B c = 2 7 __ c 1 4 1 4 2 7 _____ 1 7 2 1 14 __ Substitute for c. 2 7 __ Use the GCF to simplify. The answer is in simplest form. 1 2 1 4 __ 2 7 Multiply.

19. Course 1 5-7 Multiplying Fractions Check It Out: Example 2C c = 4 7 __ c 1 4 1 4 4 7 _____ 4 1 7 4 4 28 __ Substitute for c. 4 7 __ Multiply. The GCF of 4 and 28 is 4. The answer is in simplest form. 1 7 __

20. Course 1 5-7 Multiplying Fractions Lesson Quiz Multiply. Write each answer in simplest form. 1. 2. Evaluate the expression x for each value of x. Write the answer in simplest form. 3. x =4. x = 5. At a particular college of the students take a math class. Of these students, take basic algebra. What fraction of all students take basic algebra? 3 5 __ 1 4 5 7 __ 3 10 __ 1 8 __ 4 5 1 8 2 5 1 4 3 20 __ 3 14 __ 1 10 __ 1 64 __ 1 10 __