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Calculating Volume of Cylinders, Cones, Pyramids, and Spheres

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Introduction to Volume of Solid Figures

Volume measures the amount of space inside a solid figure and is expressed in cubic units (e.g., cubic cm, cubic m).

Understanding Volume Relationships

  • Cone and Cylinder: It takes exactly three cones to fill a cylinder of the same radius and height.
  • Sphere and Cylinder: A sphere occupies 2/3 of the volume of a cylinder with the same radius and height.
  • Pyramid and Prism: It takes three pyramids to fill a prism with the same base and height. For more details, see Understanding Similar Figures and Triangles: A Comprehensive Guide.

Volume Formulas

Cylinder

  • Formula: ( V = \pi r^2 h )
  • Where ( r ) is radius, ( h ) is height, and ( \pi \approx 3.14 )

Cone

Pyramid

  • Formula: ( V = \frac{1}{3} \times \text{Base Area} \times h )
  • For rectangular base: Base Area = length ( \times ) width

Sphere

  • Formula: ( V = \frac{4}{3} \pi r^3 )

Sample Problem Solutions

1. Volume of a Cone Hat

  • Diameter: 5 cm; Height: 10 cm
  • Radius: 2.5 cm
  • Calculation: ( V = \frac{1}{3} \times 3.14 \times 2.5^2 \times 10 = 65.42 ) cubic cm

2. Volume of a Cylindrical Candle

  • Diameter: 12 cm; Height: 18 cm
  • Radius: 6 cm
  • Calculation: ( V = 3.14 \times 6^2 \times 18 = 2,034.72 ) cubic cm

3. Volume of a Rectangular Base Pyramid (Glass Keychain)

  • Base: 3 cm by 4.5 cm; Height: 6 cm
  • Base Area: 13.5 cm2
  • Calculation: ( V = \frac{1}{3} \times 13.5 \times 6 = 27 ) cubic cm

4. Volume of a Sphere

  • Radius: 8 cm
  • Calculation: ( V = \frac{4}{3} \times 3.14 \times 8^3 = 2,143.57 ) cubic cm

Additional Practice Problems

Key Points to Remember

  • Volume units are always cubic (e.g., cubic meters, cubic inches)
  • Use the proper formula depending on the solid figure
  • Convert diameter to radius by dividing by 2 when needed
  • Multiply radius by itself (square) for cylinder and cone base area calculations
  • Multiply radius by itself three times (cube) for sphere volume calculations

Mastering these concepts will enable you to confidently find volumes for a variety of solid figures and solve both routine and non-routine math problems effectively. To strengthen your measurement accuracy, consider reading Understanding Significant Figures in Measurements.

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