Teaching for Understanding Division with Fractions Dr. DeAnn Huinker, Dr. Kevin McLeod, Dr. Henry Kepner University of Wisconsin-Milwaukee Math Teacher Leader (MTL) Seminar Milwaukee Public Schools June 2005 This material is based upon work supported by the National Science Foundation Grant No. EHR
Session Goals Deepen conceptual understanding of division with fractions. Examine “why” we can invert and multiply.
Popcorn Party Serving Size: 2 cups How many servings from: 8 cups of popcorn 5 cups of popcorn
Summarize Write the equation for each situation (8 cups; 5 cups). Identify the meaning of each number in the equations.
Summarize How many 2–cup servings? 8 ÷ 2 = 4 cups cup servings serving 5 ÷ 2 = 2 cups cup serving 1212 servings
What does the represent? One-half of a cup of popcorn? One-half of a serving? Are you sure? 1212
Popcorn Party Serving Size: cup How many servings from: 1 cup of popcorn 4 cups 2 cups
Summarize How many 2–cup servings? 1 ÷ = 2 cup servings 4 ÷ = 8 cups servings 1212 cup serving 1212 cup serving
Task Popcorn Parties # 1 & # 2 æFacilitator æPaper Strip Demonstrator
Algorithm
Task Popcorn Parties # 1 & # 2 Facilitator poses one problem at a time. Each individual silently solves it. On facilitator’s cue: State answer. Demonstrator models with paper strips. Take turns to justify your reasoning.
Popcorn Party #1 Serving Size: cup of popcorn How many servings can be made from: 1 cup of popcorn 2 cups of popcorn 3 1/2 cups of popcorn 1414
Popcorn Party #2 Serving Size: cup of popcorn How many servings can be made from: 3/4 cup of popcorn 6 cups of popcorn 2 1/4 cups of popcorn 4 1/2 cups of popcorn 3434
Popcorn Party Serving Size: cup How many servings from 4 cups? 3434
Summarize How many 2–cup servings? 4 ÷ = cups 3434 cup serving
Discussion In reviewing these division situations and your solutions, what are you noticing?
Fraction Division Algorithm Photo Sequence from Session
7 X = 1 ?
a X = 1 ? Multiply by the inverse, which is also called the reciprocal.
a X = 1 a ≠ 0 Is this true for any number? What about zero? 1a1a
3434 X = 1 1 ?
7 ÷ 8 = How else can we write this?
12 24 = ? ? 1212
=
5 ÷ = 3434 Estimate Greater than 5? Equal to 5? Less than 5?
Summarize How many 2–cup servings? 5 ÷ = 3434 How else can we write this?
5 =
=
= cdcd 1 abab