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How to find Surface Area and Volume of Composite Figures

Here, you’re going to look at composite figures in 3D. In order to calculate the volume of such composite figures, you have to separate the figure into smaller figures so that you know the volume of each, and add them up.

Example 1

Example of calculation of composite figure in 3D 1

Find the volume of the composite figure

You can separate the figure into a cylinder and a cone, and find the volume of each of them.

Volume of the cylinder:

V = πr2h = π 62 9 1017.88cm3

Volume of the cone:

V = πr2h 3 = π 62 5 3 188.50cm3

Volume of the whole figure:

V = 1017.88 + 188.50 = 1206.38cm3

Example 2

Example of calculation of composite figure in 3D 2

Find the volume of this ice cream

Half of the scoop of ice cream is inside the wafer. The volume of the wafer is the volume of a cone:

V cone = π 42 15 3 251.2cm3

The volume of the entire scoop of ice cream is the volume of a sphere:

V sphere = 4 π 43 3 267.95cm3

If you now add the volume of the scoop of ice cream to the volume of the cone, you will be adding the entire ice cream scoop. But half of the scoop is inside the wafer cone, so to not count that volume twice, you have to divide the volume of the sphere by 2. Then you can add it to the volume of the cone to find the total volume of the ice cream.

The volume of the entire ice cream is

V = 251.2cm3 + 267.95cm3 2 = 385.18cm3

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