L3 · Nets and surface area

1. 1.

   A rectangular prism has length 4 cm, width 2 cm, and height 5 cm. Use a net (or the faces) to find the surface area.

   Answer. 76 square cm

   SA = 2(ℓw + ℓh + wh) = 2(8 + 20 + 10) = 76 square cm.

2. 2.

   A rectangular prism has length 4 cm, width 6 cm, and height 5 cm. Use a net (or the faces) to find the surface area.

   Answer. 148 square cm

   SA = 2(ℓw + ℓh + wh) = 2(24 + 20 + 30) = 148 square cm.

3. 3.

   A rectangular prism has length 9 cm, width 7 cm, and height 4 cm. Use a net (or the faces) to find the surface area.

   Answer. 254 square cm

   SA = 2(ℓw + ℓh + wh) = 2(63 + 36 + 28) = 254 square cm.

4. 4.

   A rectangular prism has length 4 cm, width 5 cm, and height 2 cm. Use a net (or the faces) to find the surface area.

   Answer. 76 square cm

   SA = 2(ℓw + ℓh + wh) = 2(20 + 8 + 10) = 76 square cm.

5. 5.

   Elena wraps a gift box 5 cm by 6 cm by 4 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

   Answer. 148 square cm

   SA = 2(30 + 20 + 24) = 148 square cm.

6. 6.

   Luis wraps a gift box 5 cm by 3 cm by 3 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

   Answer. 78 square cm

   SA = 2(15 + 15 + 9) = 78 square cm.

7. 7.

   Theo wraps a gift box 6 cm by 3 cm by 6 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

   Answer. 144 square cm

   SA = 2(18 + 36 + 18) = 144 square cm.

8. 8.

   Elena wraps a gift box 6 cm by 5 cm by 6 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

   Answer. 192 square cm

   SA = 2(30 + 36 + 30) = 192 square cm.

9. 9.

   Malik wraps a gift box 8 cm by 6 cm by 6 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

   Answer. 264 square cm

   SA = 2(48 + 48 + 36) = 264 square cm.

10. 10.

    Nora wraps a gift box 9 cm by 7 cm by 4 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

    Answer. 254 square cm

    SA = 2(63 + 36 + 28) = 254 square cm.

11. 11.

    Think

    Malik found the volume 24 instead of the surface area of a 3 by 4 by 2 cm box. What is the surface area?

    Answer. 52 square cm

    Volume uses ℓwh. Surface area adds faces: 2(12 + 6 + 8) = 52 square cm.

12. 12.

    Think

    Malik found the volume 105 instead of the surface area of a 3 by 7 by 5 cm box. What is the surface area?

    Answer. 142 square cm

    Volume uses ℓwh. Surface area adds faces: 2(21 + 15 + 35) = 142 square cm.

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