Multiplication Strategies for Larger Numbers

Students built a class menu for multiplication strategies in Unit 4 Lesson 10. In that activity, students identified strategies for solving a 2-digit by 1-digit multiplication problem. Tell students that they will do the same for multidigit by 1-digit multiplication problems.

Ask students to solve 519 × 4 using two different strategies. For one of the solutions, ask students to choose a mental math strategy. Two possible strategies involving mental math are shown in Figure 1.

Ask students to share their solutions with the class and record them on the board or chart paper as a class menu. Once a student has shared a solution, ask another student to share a different strategy. If a student shares a mental strategy, identify it as a mental strategy by putting a cloud around the solution.

Remind students that sometimes when solving a problem using mental math, it makes it easier to write down an intermediate step. For example, in this problem, a student may mentally partition 519 into 500 + 19, jot down 2000 for the 4 × 500, and then use mental strategies to multiply 4 × 19.

After you have several different strategies or methods for solving 519 × 4, ask students to pull out the Multiplication Strategies Menu for Larger Numbers from their Student Activity Books. See Figure 2. Compare it to the strategies collected for your class menu. Check to see if students used each of the strategies on the menu. If a strategy was not used, ask students to solve 519 × 4 using that strategy. Label the strategies on the board or chart paper with the corresponding strategy names from the menu.

Students also have a blank strategies menu, My Multiplication Strategies Menu in their Student Activity Books. Encourage them to use this page to write down other strategies or one from the class. Students can also write a full strategies menu to leave at home for reference.

Assign the rest of the problems in the Homework section at this time.