L25 · Area and surface area

1. 1.

   Find the area of the parallelogram.

   Answer. 40 square in

   A = b × h = 8 × 5 = 40 square in.

2. 2.

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

   Answer. 168 square cm

   SA = 2(ℓw + ℓh + wh) = 2(24 + 24 + 36) = 168 square cm.

3. 3.

   Find the area of the parallelogram.

   Answer. 60 square m

   A = b × h = 15 × 4 = 60 square m.

4. 4.

   A rectangular prism has length 6 cm, width 4 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 + 30 + 20) = 148 square cm.

5. 5.

   Owen cuts a parallelogram with base 5 cm and height 11 cm from paper, then cuts an identical second one. What is the total paper area used?

   Answer. 110 square cm

   One parallelogram is 55 square cm. Two of them: 110 square cm.

6. 6.

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

   Answer. 148 square cm

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

7. 7.

   Malik cuts a parallelogram with base 11 m and height 12 m from paper, then cuts an identical second one. What is the total paper area used?

   Answer. 264 square m

   One parallelogram is 132 square m. Two of them: 264 square m.

8. 8.

   Jonah wraps a gift box 7 cm by 4 cm by 3 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

   Answer. 122 square cm

   SA = 2(28 + 21 + 12) = 122 square cm.

9. 9.

   Sam cuts a parallelogram with base 8 cm and height 9 cm from paper, then cuts an identical second one. What is the total paper area used?

   Answer. 144 square cm

   One parallelogram is 72 square cm. Two of them: 144 square cm.

10. 10.

    Sam wraps a gift box 8 cm by 2 cm by 3 cm. Ignoring overlap, how much wrapping paper covers the whole surface?

    Answer. 92 square cm

    SA = 2(16 + 24 + 6) = 92 square cm.

11. 11.

    Think

    Mei used the slanted side 16 instead of the height 7 and got 224. What is the actual area of a parallelogram with base 14 in and height 7 in?

    Answer. 98 square in

    Height is perpendicular, not slanted. A = 14 × 7 = 98 square in.

12. 12.

    Think

    Priya found the volume 140 instead of the surface area of a 7 by 4 by 5 cm box. What is the surface area?

    Answer. 166 square cm

    Volume uses ℓwh. Surface area adds faces: 2(28 + 35 + 20) = 166 square cm.

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