## Regrouping to Multiply and Divide: Tips and Tricks

• Do a quick warm-up activity each day to reinforce multiplying with multiples of 10 and 100. Have the class count the number of times a volunteer can bounce a ball, jump up and down, or perform some other activity in one minute. Then have the class use mental math to find the number of times the activity could be performed in 20 minutes, 300 minutes, and so on.
• Set up a general store in your classroom. Have students bring in empty containers from home. Students can make multiple purchases of individual items and use play money—\$1 bills, dimes, and pennies—to model the multiplication for finding the total amount of the purchase.
• Challenge students by giving them the product of a one-digit factor multiplied by a two-digit factor and having them find the factors.
• Have students work in groups of 3 or 4 for this activity. Give each group a multidigit multiplication problem to solve. Each member of the group chooses a different method to find the product, such as modeling with base-ten blocks, drawing arrays, using addition, and so on. Have students share their methods with the class.
• Base-ten blocks can be an excellent demonstration tool and powerful manipulative for teaching regrouping for multiplication and division. If commercial blocks are not available, paper sets can be made from posterboard or construction paper, or use Learning Tools 23 and 24 in the Learning Tools Folder.
• Label the dividend, divisor, and quotient for both forms of division and post them as models in the classroom.
• Provide students with square grid paper (Learning Tool 36 in the Learning Tools Folder) to use when they divide. This will help them align digits in the correct places.
• Have students do this activity in groups of 3. Each student rolls a 1−6 number cube once. They use the numbers rolled as digits to make and solve different division problems with two-digit dividends and one-digit divisors.
• Have students check each other's division by multiplying. This may seem less tedious to students because they are not repeating their own work. Students may also see it as a challenge to find another student's errors.