Lesson 11 Subtract Fractions Flexibly

    • Let’s find all kinds of differences.

Warm-up Which One Doesn’t Belong: Fractional Values

Which one doesn’t belong?

Activity 1 Friendship Bracelets

image of macramé friendship bracelet

Clare, Elena, and Andre are making macramé friendship bracelets. They’d like their bracelets to be inches long. For each question, explain or show your reasoning.

  1. Clare started her bracelet first and has only inch left until she finishes it. How long is her bracelet so far?

  2. So far, Elena’s bracelet is inches long and Andre’s is inches long. How many more inches do they each need to reach inches?

  3. How much longer is Elena’s bracelet than Andre’s at the moment?

Activity 2 Multiple Ways to Subtract

Problem 1

Here are four expressions that you may have written about the friendship bracelets.

Here is one way to find the value of the first expression. Analyze the calculation. Talk to your partner about why is written as different sums.

Subtract. 9 and 4 eighths minus 7 eighths.

Problem 2

Here are some unfinished calculations. Complete them to find the value of each difference.

  1. Subtract. 9 and 4 eighths minus 5 and 1 eighth. Under first number. Line 1, 9 and 4 eighths. Line 2, 9 plus 4 eighths. Under second number. Line 1, 5 and 1 eighth. Line 2, 5 plus 1 eighth.
  2. Subtract. 9 and 4 eighths minus 3 and 5 eighths.
  3. Subtract. 5 and 1 eighth minus 3 and 5 eighths.

Practice Problem

Problem 1

Elena is making friendship necklaces and wants the chain and clasp to be a total of inches long. She is going to use a clasp that is inches long. How long does her chain need to be? Explain or show your reasoning.