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Volume of prisms
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The volumes of various 3D shapes can be calculated by using their respective formulae.
A prism is a 3D shape that is a 2D shape stretched in the third dimension. The 2D shape is called it's cross-section.
This is a prism with a cross-section that is a hexagon. Therefore, this shape is called a hexagonal prism.
This is a prism with a cross-section that is a triangle. Therefore, this shape is called a triangular prism.
A cylinder is also a type of prism, it has a circular cross-section.
Here are the 3D shapes that you need to be able to calculate the volumes of:
SHAPE
FORMULA
DIAGRAM
Cube
V=x×x×x=x3V=x\times x\times x=x^3V=x×x×x=x3
Where xxx is the length of a single side.
Cuboid
V=length×width×heightV=\text{length}\times\text{width}\times\text{height}V=length×width×height
V=lwhV=lwhV=lwh
Cylinder
V=π×radius2×heightV=\pi \times \text{radius}^2\times \text{height}V=π×radius2×height
V=πr2hV=\pi r^2 hV=πr2h
Prism
V=A×lV=A\times lV=A×l
Where AAA is the area of the cross-section, and lll is the length.
A prism has a cross-sectional area of 7.5cm27.5cm^27.5cm2 and a length of 12cm12cm12cm. What is the volume of the prism?
Substitute A=7.5A=7.5A=7.5 and l=12l=12l=12 into the formula:
V=A×l=7.5×12=90\begin{aligned}V&=A\times l\\&=7.5\times12\\&=90\end{aligned}V=A×l=7.5×12=90
The volume of the prism is 90cm3‾\underline{90cm^3}90cm3.
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The volume of a cuboid is length x width x height.
The volume of a prism can be found by multiplying the area of its cross-section by its length.
A prism is a 3D shape that is a 2D shape stretched into the third dimension.
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