16.2 Finding the volume of compound (composite) solids
Worked example
A storage container is in the shape of a hemisphere supported on a cylindrical base, as shown in the diagram. The diameter of the hemisphere and of the cylinder is 21 cm.
The height of the cylindrical base is 42 cm. By letting π = 3.14, fi nd the volume of the container. Give your answer to two decimal places.
Solution 21 cm 42 cm
By the end of this section you should be able to:
● calculate the volume of compound (composite) shapes
Many objects are a combination of more than one shape. To fi nd the total volume of combined shapes, fi nd the volume of each regular shape and then add them up.
Practice questions 16.2
1. A basketball with a diameter of 24 cm is packaged in a box that is in the shape of a cube. The edge length of the box is equal to the diameter of the basketball. Assume no cardboard overlaps. Calculate, to the nearest whole number, the following:
(i) the surface area of the closed box (ii) the volume of the box (iii) the surface area of the basketball (iv) the volume of the basketball (v) the percentage of space in the box that is unoccupied.
2. The shape shown here was made by attaching a hemisphere to the top of a cylinder. The radius of the base of the cylinder is 2 ⋅ 3 m and the height of the cylinder is 5 ⋅ 6 m. Find the volume of the shape to the nearest whole number. (Let π = 3 ⋅ 14)