Fraction Action
COMPUTATION 6.2 - Compute Using Fractions
6.3.3 Multiply common or mixed fractions
6.3.4 Divide common or mixed fractions
Debby Gosnell
Goal/Objectives:
- Students will review fraction names and equivalent fractions
- Students will review multiplication as repeated addition
- Students will learn that multiplication of fractions involves finding a "part of a part" and does not correlate to repeated addition
- Students will learn how to multiply fractions
- Students will learn that division is multiplication of the inverse
- Students will divide fractions
Introduction:
Teacher tells candy bar story:
"I bought a candy bar at the store and when I got home my daughter asked if she could have some. Because I'm so generous, I gave her half of my candy bar. I picked up my magazine and was ready to sit down and eat what
was left of my candy bar when the doorbell rang. Two of my friends stopped by to chat. They looked hungry and I wanted to be polite, so I broke my piece of candy bar into three parts and gave a piece to each of my friends. My friends finally left and I thought now I could eat the bit of candy bar that I had left. Just before I could put the candy in my mouth, my husband came along. I knew how much he loves chocolate, so I broke my piece in half and gave him a part. I decided I'd better hurry and eat the remaining portion before any more hungry people came along, and I quickly popped the chocolate into my mouth!
How much of the original candy bar did I end up with?"
We'll come back to that question in a little bit. First, I'm going to give all of you a candy bar, and I'll let you try out some fraction action yourselves!
Main Activity:
- Teacher will model activities using overhead projector
- Students can work individually or in groups
- Using "candy bar math", students will represent:
- different fraction amounts
- equivalent fractions
- multiplication as repeated addition
- Using paper version of candy bar and colored plastic overlays representing fraction pieces, students will solve multiplication problems involving fractions
- Teacher will introduce division as "how many ____ will fit in_____" students will use fraction pieces to solve
- Teacher will introduce division as multiplication of the inverse students will solve fraction division problems
Closure/conclusion:
Come back to the candy bar story and have students work out the problem together, either using the actual candy bars or the paper models. Have students help determine the math equations to represent the problem.
|
One-half of the original candy bar: |
1/2 |
| One-third of that amount... | |
| This is what was left after giving two pieces to friends | 1 X 1 = 1 |
| 3 X 2 = 6 | |
| One half of that amount | 1 X 1 = 1 |
| remained after sharing with my husband | 2 X 6 = 12 |
Follow-up Lessons and Activities / Real-life Connections:
#1
- Teacher and/or students bring in recipes
- Change recipe to the amounts needed for one-third the original recipe
- Do the same for other amounts: 3 and a half; one-fourth; etc.
- Using actual measuring cups and measuring spoons, lead students to
the discovery of any problems with their
conversions
(For example: how would we measure one-fourth of a Tablespoon or one-twentieth of a cup?) - Have students use a dry ingredient (sugar, or cornmeal, ... or you
could even use sand) and figure out how to
represent "odd measures" such as those mentioned above. Use a dishpan or small tub to measure over. - Have students come up with a conversion chart:
- For example: 4 Tablespoons = one-fourth cup
- Make one of the converted recipes
#2
- Using actual plans for an item such as a shelf, a bookcase, or a chair, figure the proportions needed to make that item to scale: such as one-tenth the original size
- Make items for a dollhouse using the plans