To find the volume of each hole, consider a prism with the same dimensions of the hole.
See solution.
Practice makes perfect
Let's begin by drawing the concrete block given in the mentioned example.
To find the volume of the concrete block, we will use the Volume Addition Postulate.
The volume of a solid is the sum of the volumes of all its nonoverlapping parts.
Using this postulate, we will find the volume of the concrete block by subtracting the volume of each hole from the volume of the large rectangular prism.
The base of the prism above is a rectangle. Then, its area is the product of the width and the length. Also, we see that its height is 0.66 ft. We are ready to find its volume.
The volume of the large rectangular prism is about 0.5706 ft^3. Next, let's draw the prisms representing the two holes.
Since both prisms have the same dimensions, their volumes are equal. It is enough to find the volume of one of them and multiply it by two. We will proceed as before.
Consequently, the volume of the concrete block is about 0.40 ft^3, which is the same result that we obtained in the mentioned example. As we can see, both methods are quite similar and it is up to you which method to use.
