Composite Solid Volume Calculation

00:00 8 marks

  • Build Confidence
  • SL & HL
  • Tier 3
  • Composite solids
  • Spatial reasoning
  • Volume formulas

A new community center features a unique design with a composite interior space. The design includes:

– A main hall in the shape of a rectangular prism with dimensions: length = 10 m, width = 8 m, and height = 4 m.
– A hemispherical dome placed on top of the hall, with a radius of 4 m.
– A conical skylight removed from the center of the dome with a height of 2 m and a base radius of 1.5 m.

Determine the overall interior volume of the community center considering the removed skylight.

Break your work into three parts:
(a) Identify the basic geometric solids in this composite figure.
(b) Calculate the total volume of the interior space (volume of the rectangular prism plus the hemisphere, minus the cone volume).
(c) Interpret the result by discussing how the removed skylight affects the total volume and its implications in real-world planning.

Part a

3 minutes 2 marks

Question

Identify the basic geometric shapes that make up the composite structure of the community center.



Hint Hint

Hint

List each solid involved in the design.

  • Answer Answer

Complete Answer

Rectangular prism, hemisphere, and cone.

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Part b

5 minutes 4 marks

Question

Calculate the total volume of the interior space using the given dimensions:

– Rectangular prism: length = 10 m, width = 8 m, height = 4 m
– Hemisphere: radius = 4 m
– Cone (skylight): height = 2 m, radius = 1.5 m

Provide your answer in cubic meters (\(m^3\)) to one decimal place.



Hint Hint

Hint

Calculate each volume separately then combine: Total Volume = Volume of Prism + Volume of Hemisphere – Volume of Cone.

  • Answer Answer

Complete Answer

449.5 m^3

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Part c

3 minutes 2 marks

Question

Interpret the result by explaining how the removal of the conical skylight affects the overall volume, and discuss the potential implications for the community center design in terms of natural lighting versus volume and material usage.



Hint Hint

Hint

Consider the trade-offs between natural light, heating/cooling volume, and construction material.

  • Answer Answer

Complete Answer

Removing the skylight reduces the total volume, potentially decreasing heating/cooling costs but increasing material for the dome. It also introduces natural light, which can reduce electricity use.

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