1
Multiplication and Division
The Mystery of the Mixed-Up Party Lists
Meet the Fact Family
Guess-timate Estimates
Point and Play
200 Catch Game
Blocks of Division
Words of Division
Divisibility Dash
Scuba Division
Show the Order
THE MYSTERY OF THE MIXED-UP PARTY LISTS
Objective
Students will work in groups to find the least common multiple.
Anticipatory Set
Speaking with the excited tone of a news reporter, announce to students, “Eight girls and boys were each planning their own birthday party. Each person was carrying a party list with the number of guests. They were all shopping at the same store to buy party supplies when suddenly the lights went out! Somehow, their party lists got mixed up. They don’t remember how many guests are invited or how many supplies to buy. It is your job to help solve the mystery!”
Purpose
Tell students that they are detectives needed to solve a mystery. Their job is to use clues to figure out the number of guests each boy or girl invited to his or her party and exactly how many of each item to buy.
Input
Tell students that they will be working with multiples as clues: “A multiple of a number is the product of that number and another whole number.” On the board, write two tables with examples of multiples. Across the top row of each table, write the numbers 1 through 12. Across the bottom row of the first table, write multiples of 3 up to 36. Across the bottom row of the second table, write multiples of 5 up to 60.
Explain that the least common multiple is the smallest number into which two numbers can both be evenly divided. One way to find the least common multiple of two numbers is to make two tables. One table lists the multiples of one number. The other table lists the multiples of the other number. Compare the two tables with students, and circle the smallest number that appears on both lists. Explain that 15 is the least common multiple for the numbers 3 and 5.
Modeling
Divide the class into eight small groups. Place a transparency of a multiplication table on the overhead projector, and give each student a photocopy. Review the table so students understand how to use it.
Provide an example so students can create their own tables. Say, “Pretend we are going to the store to buy prizes for a party. Toy cars come in packages of four. Balloons come in packages of seven. We want to buy the same number of toy cars and balloons. To help us find this number, we can draw two tables of multiples.”
Distribute ½-in (1.27 cm) graph paper to students. On the board, draw two tables with two rows each. Have students copy the tables onto their graph paper. Across the top of one table, write the numbers 1 through 12. Label this row “Packages of Toy Cars.” Across the bottom row, ask volunteers to suggest multiples of 4 for you to write. Encourage students to refer to their multiplication table as a guide. Label this row “Total # of Cars.”
Draw a similar table for the packages of balloons, using multiples of 7. Have students copy the second table onto their graph paper. After both tables are completed, ask students to circle the smallest number in both tables. Ask, “What is the least number of packages of toy cars we need to buy?” (7), “What is the least number of packages of balloons we need to buy?” (4), and “What is the least common multiple of 7 and 4?” (28)
Checking for Understanding
Check to make sure students know how to draw tables comparing two multiples. Remind them that the least common multiple is the smallest number in both tables.
Guided Practice
Give each group a party gift bag. Each bag should contain one of eight cards cut from the Shopping List Cards reproducibles. Inform groups that the clues they need to solve the mystery are in the gift bags. Instruct them to read the clues and make two tables of multiples on their graph paper. Students will use the information from these tables to answer the questions and solve the mystery of the mixed-up party lists.
Closure
Afterward, ask each group to read aloud its clues, report its answers, and explain how its members reached their conclusions. Then ask students to reflect on what they learned in their math journals.
Independent Practice
Place the gift bags at a math center with multiplication tables, graph paper, and pencils. Invite students to visit the center and solve the mystery of the mixed-up party lists following the clues in other groups’ gift bags. Number each gift bag, and provide a self-check by writing the answers to each card on the bottom of the corresponding bag.
Shopping List Cards 1–4
Shopping List Cards 5–8
MEET THE FACT FAMILY
Objective
Students will work in groups to identify fact families for sets of numbers.
By simply adding a visual representation of a situation that is relevant to students, greater meaning can be obtained.
Anticipatory Set
Draw two rows of three triangles on the board. Ask volunteers to state a multiplication equation that describes the triangle arrangement (2 × 3 = 6 or 3 × 2 = 6). Write both equations on the board. Repeat the activity, and ask students to state a division equation that describes the triangles (6 ÷ 2 = 3 or 6 ÷ 3 = 2). Write both equations on the board.
Purpose
Ask for a volunteer who has four family members. Make a chart on the board. Write that student’s last name at the top of the chart. Underneath, list the four family members’ names.
Make a second chart on the board. At the top of the chart, write the numbers 2, 3, and 6. Explain to students that just as each of them has a family, each set of numbers has a family called a fact family. Say, “A fact family shows the multiplication and division equations that can be written for a set of numbers.” On the chart, list the four equations for the fact family 2, 3, and 6.
The Lee Family |
Mr. Lee |
Mrs. Lee |
Eric |
Mina |
The Fact Family for 2, 3, and 6 |
2 × 3 = 6 |
3 × 2 = 6 |
6 ÷ 2 = 3 |
6 ÷ 3 = 2 |
Input
Tell students, “Learning fact families will help you to multiply and divide. Just as identifying people in a family helps us see how they are related, identifying the f...