LESSON 11 Workshop: Multiply and Divide Fractions

Fern's Mistake

Fern and Mara are talking about multiplying and dividing fractions.

Fern explains, “I thought about the denominator in the same way as I did when I added or subtracted fractions. I found a common denominator, 12. Then instead of adding or subtracting, I multiplied the numerators.”

1. Talk with a partner. What did Fern do incorrectly in the problem below?

= =

Compare Addition and Multiplication

Mara uses fraction circle pieces to model + .

“When you are adding, you are counting parts of a whole, so those parts have to be the same size, like twelfths. But when you multiply, you are finding a part of a part, so the part may change size,” Mara explains.

Self Check: Questions 2–4

1. Use fraction circle pieces, a rectangle, or number line to model and solve .
2. Write your answer in simplest form. How do you know it is in simplest form?