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Check-In: Questions 1–3
- Find a different mental math strategy to solve one of the problems Mrs. Dewey wrote. Explain your method.
- Will everyone choose to use the same method for each problem? Explain.
- Nicholas used money to solve 26 4. Does this strategy work well for 38 10? Why or why not?
Compare your strategies to those on the Multiplication Strategies Menu in the Student Activity Book.
Paper-and-Pencil Methods
Mrs. Dewey decided to use some of the multiplication problems on the board to review paper-and-pencil multiplication. Mrs. Dewey selected 5 22. She drew a rectangle and filled it in as shown below.
Mrs. Dewey broke apart 22 into 20 + 2. She multiplied the 5 20 and got 100. Then she multiplied the 5 2 and got 10. Finally she added 100 + 10 to get 110.
Check-In: Questions 4–5
- Explain how Mrs. Dewey's method is similar to the expanded-form method that Grace used to solve this problem. Show where each number in each method comes from.
- Solve these problems in two ways. First use rectangles. Use Half-Centimeter Grid Paper from the Student Activity Book to organize your work. Then use the expanded-form method.
- 27 7
- 38 8
- 42 9