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Odd One Out
Students will be able to determine whether a group of objects has an even or odd number of items using a variety of problem-solving methods.
- Call students together. Dump out one of the sandwich bags. Ask students to determine how many items there are.
- Next, ask students to think about different ways that the items can be sorted, such as color and size.
- Tell students that there is another way that people sometimes sort things. Explain that objects can be sorted into even and odd numbered groupings.
- Explain to your students that even numbers are those that can be divided by two, so there will be none left over if the group of objects is paired off.
- Tell your students that odd numbers are those that can’t be divided by two, so there will be one left over if an odd numbered group of objects is paired off.
Explicit Instruction/Teacher modeling(5 minutes)
- Demonstrate how to line the objects up into two straight matching lines. If there is an object left over, explain to students that this means that the number is odd. If the end result is just equal pairings, point out that the number is even.
- Ask students if they can think of any other ways to quickly determine if there will be equal numbers of pairs.
- Suggest that students could count the number of objects by twos to determine if there will be one left over.
- Have students brainstorm a list of ideas for determining whether or not there will be an equal number of pairs. Post this list in a prominent location.
- Use another sandwich bag of objects to demonstrate the process again.
- Have students first count the number of objects.
- Then, ask them to pair up objects, count by twos, or use some other method to determine if one will be left over.
- After doing this, guide students to say whether the group is odd or even.
Guided Practice(10 minutes)
- Pass out pens and pencils along with sheets of paper.
- Have students draw four columns on their papers. Direct them to label each column with Number of Objects, My Guess, Odd/Even, and Method Used.
- Demonstrate to students that when they get a bag, they should dump it out and count the objects. Then, instruct them to record this number in the Number of Objects column.
- Next, direct your students to record their guesses about whether or not the number is odd or even in the My Guess column.
- After this, ask them to choose a method from the class generated list and determine whether or not the number of objects is odd or even. Have them record this in the Odd/Even Column and the method used in the Method Used column.
Independent working time(10 minutes)
- After modeling this process, have students try it with partners a few times.
Enrichment: To create more of a challenge, have students start to combine small groups of identified odd and even numbered objects. Raise a discussion: "Is the new amount odd or even? Which groups can be combined to make odd numbers? Which ones will make even numbers?"
Support: Post a list of potential methods for determining whether the amount of objects is odd or even. Make the charts in advance for the students to fill out so that students can focus on just making sure it is filled in correctly. Have your students work in pairs.
- Walk around while your students are counting, making sure that they are using a method rather than counting the objects one by one.
- Send students home with objects to repeat the activity for homework. If students fill out charts again for homework, these can be used to monitor progress and determine whether learning objectives have been met.
Review and closing(5 minutes)
- Call students together.
- Have students take turns discussing their experiences. Potential questions include: "What was the easiest method for determining if a group of objects was odd or even? What was the fastest method? Did you figure out a way to correctly predict whether a number would be odd or even?"
- Encourage students to look around the room and find other groups of objects and identify them as odd or even.
- Close by reminding students that even numbers are able to be divided equally by two, and odd numbers are not able to be divided equally by two.