1. Grade 8 Surface area 1
CONFIDENTIAL

2. The surface area of a rectangular solid is expressed in square units.
The surface area of a solid figure is the sum of the areas of all faces of the figure.
An area of study closely related to solid geometry is nets of a solid. Imagine making cuts along some edges of a solid and opening it up to form a plane figure. The plane figure is called the net of the solid.
The surface area of a rectangular solid is expressed in square units.

3. Surface Area of solid figures
In general,
Surface Area of solid figures
= 2 x area of the base +perimeter of the base x height
If,
B = area of the base
P = perimeter of the base
h = height
SA = Surface Area
Then,
SA = 2B +Ph

4. If s is the length of one of its sides, then
Cubes
A cube is a three-dimensional figure with all edges of the same length. s s
If s is the length of one of its sides, then
SA = 2(s2) + (4s)s = 6s2

5. Rectangular prism h h w w l l SA = 2B + Ph SA = 2(lw) + (2l + 2w)h
= 2(lw + lh + wh)

6. Let us do some practice problems!

7. 1) What is the surface area of the cube with length of sides = 7 cm.
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8. 2) What is the surface area of the given rectangular prism.
5.5 cm
4 cm
7cm
152 cm2
177 cm2
156 cm2
158 cm2 8
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9. 3) What is the surface area of the given rectangular prism?8 4 7
266 cm2
258 cm2
232 cm2
368 cm2
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10. 4) This net can be folded on the dashed lines to make a box
4) This net can be folded on the dashed lines to make a box. What is the surface area of the box?
306 in2.
370 in2.
360 in2.
350 in2.
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11. 5) Gina has a sheet of cardboard that measures 9 feet by 6 feet
5) Gina has a sheet of cardboard that measures 9 feet by 6 feet. She uses scissors and tape to make the entire sheet of cardboard into a closed box that is a perfect cube. What is the surface area of the box?
81 feet2
63 feet2
45 feet2
54 feet2
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12. 6) How many unit cubes would it take to fill the box with an area of 10 square feet?
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13. 7) The rectangular prism at the right is made from centimeter cubes
7) The rectangular prism at the right is made from centimeter cubes. What is the surface area of the prism?
88 unit2
77 unit2
66 unit2
76 unit2
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14. 8) What is the total surface area of the box, including the bottom and the top?
405 unit2
408 unit2
406 unit2
409 unit2
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15. 9) What is the surface area of the given box?
336 cm2
346 cm2
326 cm2
376 cm2
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16. 10) What is the surface area of the given box?
82 cm2
72 cm2
92 cm2
102 cm2
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17. Assessment

18. 1) The surface area of a cube is 24 ft2. Find the length of each edge.
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19. 2) What is the length of each edge of the box that is a perfect cube with area 54 units2?
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20. 3) What is the surface area of the given Regular square prism?8 11
470 unit2
480 unit2
490 unit2
580 unit2
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21. 4) Bill has a sheet of cardboard with an area of 10 square feet
4) Bill has a sheet of cardboard with an area of 10 square feet. He makes the entire sheet of cardboard into a closed rectangular box. The four sides of the box have the same area, and the two ends have the same area. The area of each of the four equal sides is twice the area of each end. What is the area of each face of Bill’s box?
2 unit2; 1 unit2
3 unit2; 1.5 unit2
4 unit2; 2 unit2
5 unit2; 2.5 unit2
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22. 5) What is the surface area of the given Regular square pyramid?
180 unit2
150 unit2
146 unit2
136 unit2
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23. 6) What is the surface area of the given square pyramid?
26 yd2
22 yd2
24 yd2
28 yd2
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24. 7) What is the surface area of the given rectangular pyramid?
64 in2
56 in2
45 in2
74 in2
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25. 8) What is the surface area of the given rectangular pyramid?
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26. 9) What is the surface area of the given rectangular pyramid?
92 yd2
94 yd2
96 yd2
98 yd2
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27. 10) What is the surface area of the given rectangular pyramid?
592 cm2
564 cm2
594 cm2
565 cm2
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28. You did a great job today!