L16 · Reasons for rewriting expressions

1. 1.

   A square has side x + 7. Write an expression for the perimeter.

   Answer. 4x + 28

   P = 4(x + 7) = 4x + 28.

2. 2.

   A square has side x + 8. Write an expression for the perimeter.

   Answer. 4x + 32

   P = 4(x + 8) = 4x + 32.

3. 3.

   A square has side x + 8. Write an expression for the perimeter.

   Answer. 4x + 32

   P = 4(x + 8) = 4x + 32.

4. 4.

   A square has side x + 5. Write an expression for the perimeter.

   Answer. 4x + 20

   P = 4(x + 5) = 4x + 20.

5. 5.

   A square has side x + 4. Write an expression for the perimeter. Then Elena needs 4 of that amount. What is the total they need?

   Answer. 16x + 16

   P = 4(x + 4) = 4x + 16. Then multiply by 4: 16x + 16.

6. 6.

   A square has side x + 4. Write an expression for the perimeter. Then Nora needs 4 of that amount. What is the total they need?

   Answer. 16x + 16

   P = 4(x + 4) = 4x + 16. Then multiply by 4: 16x + 16.

7. 7.

   A square has side x + 4. Write an expression for the perimeter. Then Nora needs 4 of that amount. What is the total they need?

   Answer. 16x + 16

   P = 4(x + 4) = 4x + 16. Then multiply by 4: 16x + 16.

8. 8.

   A square has side x + 9. Write an expression for the perimeter. Then Elena needs 3 of that amount. What is the total they need?

   Answer. 12x + 36

   P = 4(x + 9) = 4x + 36. Then multiply by 3: 12x + 36.

9. 9.

   A square has side x + 3. Write an expression for the perimeter. Then Priya needs 5 of that amount. What is the total they need?

   Answer. 20x + 12

   P = 4(x + 3) = 4x + 12. Then multiply by 5: 20x + 12.

10. 10.

    A square has side x + 5. Write an expression for the perimeter. Then Owen needs 2 of that amount. What is the total they need?

    Answer. 8x + 20

    P = 4(x + 5) = 4x + 20. Then multiply by 2: 8x + 20.

11. 11.

    Think

    Elena tried this problem:
    A square has side x + 3. Write an expression for the perimeter.
    Elena wrote 5x + 12. That is not correct. What is the right answer?

    Answer. 4x + 12

    Elena’s answer 5x + 12 is off. P = 4(x + 3) = 4x + 12.

12. 12.

    Think

    Sam tried this problem:
    A square has side x + 5. Write an expression for the perimeter.
    Sam wrote 8x + 20. That is not correct. What is the right answer?

    Answer. 4x + 20

    Sam’s answer 8x + 20 is off. P = 4(x + 5) = 4x + 20.

Original extra practice. Keys are computed from the items, not guessed.