Assign Check-In: Questions 1–8 on the Multiplication and Rectangles pages in the Student Guide to complete the lesson. Students will need square-inch tiles or a copy of the Centimeter Grid Paper Master.
Discuss Questions 5–7 as a class using prompts similar to those below:
- What rectangles did you make with 20 tiles? (1 × 20, 20 × 1, 2 × 10, 10 × 2, 4 × 5, 5 × 4)
- What are the factors of 20? How do you know? (1 and 20, 2 and 10, 4 and 5. Those are the numbers in the sentences in the rectangles.)
- Is 20 a prime number? How do you know? Use tiles to justify your answer. (No. You can make more rectangles than just 1 × 20 and 20 × 1.)
- Is 20 a square number? How do you know? Use tiles to justify your answer. (No. None of the rectangles we made are square. None of the multiplication sentences have the same two factors.)
- Is 13 a prime number? How do you know? Use tiles to justify your answer. (Yes. It only has two factors—1 and itself. That's because you can only make rectangles with one row or one column: 1 × 13 and 13 × 1.)
- Is 16 a square number? How do you know? Use tiles to justify your answer. (Yes, one of its rectangles makes a square and the number sentence is 4 × 4 = 16, with two 4s.)
Use Check-In: Questions 1–8 on the Multiplication and Rectangles pages of the Student Guide to assess students' progress toward the following Expectations:
- Represent multiplication and division problems with rectangular arrays and number sentences [E1].
- Use strategies to solve multiplication and division problems [E2].
- Use turn-around facts to solve multiplication problems [E4].
Use the Floor Tiler game as targeted practice.
The workshop in Lesson 10 provides targeted practice with using strategies to solve the multiplication facts.
