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Grade 8 Surface Area #2

Grade 8 Surface Area #2. Surface area. The surface area of a solid figure is the sum of the areas of all faces of the figure.

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Grade 8 Surface Area #2

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  1. Grade 8 Surface Area #2 CONFIDENTIAL

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

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

  6. Let us do some practice problems!

  7. 1) The perimeter of one face of a cube is 48 cm. What is its surface area? • 862cm2 • 864cm2 • 866cm2 • 868cm2 CONFIDENTIAL 7

  8. A B C 3ft 2ft 2ft 6ft 1ft 3ft 2ft 3ft 4ft 2) Which of the given boxes has thegreatest surface area? • Box A • Box B • Box C • All have equal surface area 8 CONFIDENTIAL

  9. 3) The bottom of a closed rectangular box has an area of 50 square centimeters. If the box is 8 centimeters high and the length is twice the width, what is the surface area of the box? • 320 cm2 • 330 cm2 • 340 cm2 • 350 cm2 9 CONFIDENTIAL

  10. 4) Each small cube in the rectangular prism below has edges of length 2 centimeters. What is the surface area of the prism in square centimeters? • 220 cm2 • 222 cm2 • 224 cm2 • 208 cm2 10 CONFIDENTIAL

  11. 5) What is the surface area of the box with the given dimensions? • 1134 cm2 • 1224 cm2 • 1194 cm2 • 1154 cm2 CONFIDENTIAL 11

  12. 30 cm 20 cm 40 cm 6) How much wrapping paper will be needed to cover the gift box shown below without any overlapping? • 5000 cm2 • 5100 cm2 • 5200 cm2 • 5300 cm2 12 CONFIDENTIAL

  13. 4 5 B 3 A C 4 2 1 7 6 4 7) Which of the following statement about the boxes is true? • Surface area of A > Surface area of B • Surface area of A = Surface area of B • Surface area of A = Surface area of C • Surface area of C < Surface area of B 13 CONFIDENTIAL

  14. 8) What is the surface area of a cube, if the area of each face of the cube is 16 ft2? • 64 ft2 • 96 ft2 • 128 ft2 • 256 ft2 14 CONFIDENTIAL

  15. 9) What isthesurface area of the given box? • 136 in2 • 124 in2 • 132 in2 • 142in2 15 CONFIDENTIAL

  16. 1ft 1ft 1ft 10) If the length of each side of the cube is doubled, how does it affect the surface area? • The surface area is increased by 2 times. • The surface area is increased by 4 times. • The surface area is increased by 6 times. • The surface area is increased by 9 times. 16 CONFIDENTIAL

  17. Assessment

  18. 1) What is the surface area of a rectangularpacking box 11 in. long, 5 in. wide, and 4 in. high. • 200 in2 • 210 in2 • 238 in2 • 230 in2 CONFIDENTIAL 18

  19. 2) What is the surface area of the given rectangular prism. • 1800 cm2 • 1900 cm2 • 2000 cm2 • 2100 cm2 19 CONFIDENTIAL

  20. 3) What total number of unit cubes would be needed to fill the given box? • 105 • 125 • 100 • 150 20 CONFIDENTIAL

  21. 1ft 1ft 1ft 4) If the given cube is cut into two equal parts, then what will be the change in total surface area? • The total surface area will decrease by 2 times. • The total surface area will decrease by 1.5 times. • The total surface area will increase by 2 times. • The total surface area will increase by 1.3 times. 21 CONFIDENTIAL

  22. 5) The perimeter of one face of a cube is 36 cm. What is its surface area? • 486cm2 • 364cm2 • 566cm2 • 268cm2 22 CONFIDENTIAL

  23. 6) What is the surface area of the given prism? • 420.5 in2 • 320.5 in2 • 430.5 in2 • 630.5 in2 23 CONFIDENTIAL

  24. 6 6 B 4 A C 6 3 2 8 7 6 7) Which of the following statement about the boxes is false? • Surface area of A > Surface area of B • Surface area of B > Surface area of C • Surface area of A > Surface area of C • Surface area of A < Surface area of B 24 CONFIDENTIAL

  25. 1ft 1ft 1ft 8) If the length of each side of the cube is tripled, how does it affect the surface area? • The surface area is increased by 2 times. • The surface area is increased by 4 times. • The surface area is increased by 6 times. • The surface area is increased by 9 times. 25 CONFIDENTIAL

  26. 25 cm 15 cm 45 cm 9) How much wrapping paper will be needed to cover the gift box shown below without any overlapping? • 4375 cm2 • 4275 cm2 • 4350 cm2 • 4075 cm2 26 CONFIDENTIAL

  27. 10) What is the surface area of the given cube? • 35.5 cm2 • 36.5 cm2 • 37.5 cm2 • 38.5cm2 27 CONFIDENTIAL

  28. You did a great job today!

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