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This cheat sheet covers the most important surface area and volume formulas for common three-dimensional shapes. Students need these formulas to solve problems involving packaging, containers, buildings, and real objects. It helps organize many similar formulas so they are easier to compare and remember. The goal is to connect each formula to the shape dimensions it uses. Surface area measures the total outside area of a solid, while volume measures the space inside it. Prisms and cylinders use the idea that volume equals base area times height, written as V=BhV = Bh. Pyramids and cones have one third of the volume of a matching prism or cylinder, written as V=13BhV = \frac{1}{3}Bh. Spheres use formulas involving π\pi and the radius, including V=43πr3V = \frac{4}{3}\pi r^{3} and SA=4πr2SA = 4\pi r^{2}.

Key Facts

  • The volume of any prism or cylinder is V=BhV = Bh, where BB is the area of the base and hh is the height.
  • The volume of any pyramid or cone is V=13BhV = \frac{1}{3}Bh, where BB is the area of the base and hh is the perpendicular height.
  • The surface area of a rectangular prism is SA=2lw+2lh+2whSA = 2lw + 2lh + 2wh, where ll is length, ww is width, and hh is height.
  • The volume of a rectangular prism is V=lwhV = lwh, and the volume of a cube is V=s3V = s^{3}.
  • The surface area of a cylinder is SA=2πr2+2πrhSA = 2\pi r^{2} + 2\pi rh, and its volume is V=πr2hV = \pi r^{2}h.
  • The surface area of a cone is SA=πr2+πrSA = \pi r^{2} + \pi r\ell, and its volume is V=13πr2hV = \frac{1}{3}\pi r^{2}h.
  • The surface area of a sphere is SA=4πr2SA = 4\pi r^{2}, and its volume is V=43πr3V = \frac{4}{3}\pi r^{3}.
  • For composite solids, add volumes of joined parts, but do not include hidden interior faces when finding outside surface area.

Vocabulary

Surface Area
Surface area is the total area of all outside faces or curved surfaces of a three-dimensional figure.
Volume
Volume is the amount of space inside a three-dimensional figure, measured in cubic units.
Base Area
Base area is the area of the face or region used as the foundation in formulas such as V=BhV = Bh.
Height
Height is the perpendicular distance from a base to the opposite face, vertex, or base plane.
Slant Height
Slant height is the diagonal height along the side of a cone or pyramid, often written as \ell.
Radius
Radius is the distance from the center of a circle or sphere to its edge, often written as rr.

Common Mistakes to Avoid

  • Using slant height instead of vertical height for volume is wrong because volume formulas for cones and pyramids require the perpendicular height hh, not \ell.
  • Forgetting the factor 13\frac{1}{3} in cone and pyramid volume is wrong because these solids have one third the volume of a matching cylinder or prism.
  • Mixing up surface area and volume units is wrong because surface area is measured in square units such as cm2\text{cm}^{2}, while volume is measured in cubic units such as cm3\text{cm}^{3}.
  • Counting hidden faces in a composite solid is wrong because surface area includes only the outside surfaces that are visible or exposed.
  • Using diameter as radius is wrong because formulas such as A=πr2A = \pi r^{2} and V=πr2hV = \pi r^{2}h require rr, and the radius is half the diameter.

Practice Questions

  1. 1 Find the volume of a rectangular prism with length 8 cm8\text{ cm}, width 5 cm5\text{ cm}, and height 3 cm3\text{ cm}.
  2. 2 Find the surface area of a cylinder with radius 4 in4\text{ in} and height 10 in10\text{ in} using SA=2πr2+2πrhSA = 2\pi r^{2} + 2\pi rh.
  3. 3 Find the volume of a cone with radius 6 m6\text{ m} and height 9 m9\text{ m} using V=13πr2hV = \frac{1}{3}\pi r^{2}h.
  4. 4 Explain why a cone and a cylinder with the same base radius and height do not have the same volume.